JP2023121182A - Cylindrical linear motor - Google Patents

Abstract

To provide a cylindrical linear motor with which it is possible to generate high thrust and prevent rattling of a magnetic field.SOLUTION: A cylindrical linear motor 1 is constructed comprising: a cylindrical field magnet 6 which has a plurality of annular permanent magnets 10a, 10b that is stacked one on another so that N and S poles are alternately arranged on an inner axial circumference; an armature 2 which is axially removably inserted into an inner circumferential side of the field magnet 6; a cylindrical barrel 7 that covers an outer circumference of the field magnet 6; a head member 9a which is attached to one opening end of the barrel 7 and faces one end 6a of the field magnet 6; a bottom member 12 which is attached to the other opening end of the barrel 7 and faces the other end 6b of the field magnet 6; a spacer 41 which is interposed between the bottom member 12 and the field magnet 6; and an O-ring 42 which is accommodated in a recess 41c that is provided to an axial end of the spacer 41, and which functions as an elastic body to bias the field magnet 6.SELECTED DRAWING: Figure 1

Description

The present invention relates to cylindrical linear motors.

A cylindrical linear motor includes, for example, a magnetic field having a plurality of permanent magnets in which S poles and N poles are arranged alternately in the axial direction, and an armature that is axially movable relative to the magnetic field. and

In the tubular linear motor constructed in this manner, the field system or the armature is used as the stator, and the field system or the armature is fixedly attached to the inner circumference of the outer cylinder on the stator side. In a conventional cylindrical linear motor, for example, the stator includes an outer cylinder, an armature inserted into the outer cylinder, a pair of side walls attached to open ends at both ends of the outer cylinder, and a pair of side walls and the armature. and a packing inserted in two places between (see, for example, Patent Document 1).

JP 2019-115171 A

In a cylindrical linear motor, when the mover is axially driven with respect to the stator to generate thrust, a reaction force of the same magnitude as the thrust acts on the armature of the stator. Since packing is provided on both end sides, all the reaction force is received by the packing.

Therefore, if the thrust force of a conventional cylindrical linear motor is increased, the packing will be crushed and the armature will move in the axial direction. In addition, when the field system is mounted on the stator side, the field system has a structure in which many magnets are laminated in the axial direction with adhesive intervening, so the axial length of the field system exposed to high heat due to long-term use may change slightly and the field may rattle in the axial direction with respect to the outer cylinder.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a cylindrical linear motor capable of generating a high thrust force and preventing rattling of the magnetic field.

In order to achieve the above object, a cylindrical linear motor according to the present invention is a cylindrical linear motor having a plurality of annular permanent magnets stacked such that N poles and S poles are alternately arranged on the inner periphery in the axial direction. a magnetic field, an armature inserted axially movably on the inner peripheral side of the magnetic field, a cylindrical barrel covering the outer periphery of the magnetic field, and a magnetic field attached to one open end of the barrel a head member facing one end of the barrel, a bottom member attached to the other open end of the barrel and facing the other end of the field, and an annular member interposed between the bottom member and the field and an elastic body that is housed in a recess provided at the axial end of the spacer and biases the magnetic field 6 .

In the tubular linear motor constructed in this manner, the magnetic field is urged by the elastic body accommodated in the concave portion of the spacer, so that the tubular linear motor is exposed to high heat due to long-term use, and the magnetic field is distorted. Even if the length in the axial direction changes slightly, the elastic body can prevent the field from wobbling in the barrel in the axial direction. In addition, since the elastic body is accommodated in the recess of the spacer facing the magnetic field, when the cylindrical linear motor generates thrust, even if the magnetic field receives the reaction force of the thrust, not only the elastic body Since the spacer also receives the reaction force, even if the thrust force of the cylindrical linear motor is increased, the displacement of the field magnet in the axial direction with respect to the barrel can be suppressed.

Also, the recess in the cylindrical linear motor may be provided at the anti-field side end of the spacer. According to the cylindrical linear motor configured in this way, the elastic body can be easily replaced during maintenance.

Furthermore, the spacer in the cylindrical linear motor may be in contact with one of the head member and the bottom member and the magnetic field when the armature is in a no-load state. According to the tubular linear motor constructed in this manner, even if a reaction force acts on the magnetic field when a thrust force is generated, the magnetic field is supported by the spacer and urged by the elastic body. Directional deviation can be effectively prevented.

According to the tubular linear motor of the present invention, it is possible to generate a high thrust force and prevent rattling of the magnetic field.

1 is a longitudinal sectional view of a cylindrical linear motor in one embodiment; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on embodiments shown in the drawings. As shown in FIG. 1, a cylindrical linear motor 1 according to one embodiment includes a plurality of annular permanent magnets 10a stacked such that N poles and S poles are alternately arranged on the inner periphery in the axial direction. 10b, an armature 2 axially movably inserted into the inner periphery of the field system 6, a cylindrical barrel 7 covering the outer periphery of the field system 6, and a barrel 7. A head portion 9a as a head member that is attached to one open end of the field magnet 6 and faces the left end 6a in FIG. A bottom cap 12 as a bottom member facing the right end 6b in FIG. and an O-ring 42 as an elastic body that is accommodated in a concave portion 41c provided at the axial end of the end-side spacer 41 and biases the magnetic field 6. As shown in FIG.

Each part of the cylindrical linear motor 1 will be described in detail below. The armature 2 includes a core 3 and windings 5 . The core 3 includes a cylindrical core body 3a and a plurality of annular teeth 3b provided on the outer periphery of the core body 3a at intervals in the axial direction.

As described above, the core 3 has a cylindrical shape, and as shown in FIG. In between there is formed a slot 4 of air gap in which the winding 5 is fitted. Further, in this embodiment, a total of nine slots 4, which are voids, are provided between adjacent teeth 3b, 3b in FIG. A wire 5 is wound around the slot 4 and mounted thereon. The winding 5 is composed of three-phase windings of a U-phase winding, a V-phase winding and a W-phase winding. In the nine slots 4, from the left in FIG. 1, W phase, W phase, W phase and V phase, V phase, V phase, V phase and U phase, U phase, U phase, U phase and W phase. is installed.

The armature 2 is attached to the outer circumference of the tip of a rod 11 that is an output shaft and is made of a non-magnetic material. The rod 11 includes a tubular first rod 20 and a tubular second rod 21 having the core 3 attached to the outer circumference thereof and screwed to the inner circumference of the first rod 20 .

The first rod 20 has a cylindrical rod body 22 having screw portions 22a and 22b on the outer periphery of the left end in FIG. 1 and the inner periphery of the right end in FIG. A rod cap 23 is screwed onto the screw portion 22a at the left end of the rod body 22 in FIG.

An annular slider 25 is fitted to the outer periphery of the right end of the rod body 22 in FIG. The slider 25 has a sliding contact portion 25a which is in sliding contact with the inner circumference of the cylindrical portion 9b, which will be described later, and an outer diameter sliding contact portion provided on the base end side of the rod 11, which is the left side of the sliding contact portion 25a in FIG. It has a small diameter portion 25b smaller than 25a, an annular groove 25c provided along the outer circumference of the small diameter portion 25b along the circumferential direction, and a flange 25d provided on the inner circumference at the right end in FIG. A seal ring 26 made of rubber as an elastic body is attached to the annular groove 25c of the slider 25. As shown in FIG. The inner diameter of the flange 25d is greater than or equal to the inner diameter of the rod body 22 and less than or equal to the outer diameter of the rod body 22. When the slider 25 is fitted to the rod body 22, the flange 25d is positioned at the right end of the rod body 22 in FIG. Abut on the surface.

The second rod 21 includes a tubular core holding tube 21a on the outer periphery of which the core 3 is mounted, and an annular slider 21b provided on the outer periphery of the tip of the core holding tube 21a, which is the right end in FIG. In addition, a threaded portion 21c is provided on the outer circumference of the base end of the core holding cylinder 21a, which is the left end in FIG. A large diameter portion 21d is provided. 1 of the rod main body 22 of the first rod 20, and screwing the threaded portion 21c into the threaded portion 22b. The rod 21 is connected. As described above, the rod 11 is configured by the first rod 20 and the second rod 21 and has a tubular shape in the present embodiment.

Further, the core 3 is fitted and attached to the outer periphery of the core holding tube 21 a of the second rod 21 . Since the outer diameter of the core holding tube 21a is smaller than the outer diameter of the rod main body 22 of the first rod 20, the second rod 21 having the armature 2 attached to the first rod 20 having the slider 25 attached thereto is attached. When connected in the manner described above, the armature 2 and the slider 25 are sandwiched between the right end of the first rod 20 in FIG. 1 and the slider 21b of the second rod 21 and fixed. When the armature 2 is attached to the rod 11 in this way, the core 3 is fixed to the rod 11 while being sandwiched between the sliders 21 b and 25 . In this embodiment, the armature 2 is configured with only a single core 3, but may be configured with a plurality of cores 3 in order to improve cogging thrust or the like.

Next, the rod 11 is provided with a cover 17 that covers the outer periphery of the rod 11 and forms a gap G. As shown in FIG. Specifically, the cover 17 has a cylindrical shape, one end of which is fitted to the outer periphery of an annular cover end 18 provided on the outer periphery of the rod 11 and the other end of which is fitted to the outer periphery of the small diameter portion 25 b of the slider 25 . and attached to the rod 11.

A gap G between the cover 17 and the rod 11 accommodates lead wires L for connecting the windings 5 of each phase attached to the core 3 to an external drive circuit (not shown). The work of wiring the windings 5 and the lead wires L can be performed in this state, and the work of assembling the cylindrical linear motor 1 is facilitated.

Next, in the present embodiment, the magnetic field 6 is composed of a plurality of annular permanent magnets 10a, which are alternately laminated in the axial direction and serve as main magnetic poles, and a plurality of annular permanent magnets 10b, which serve as auxiliary magnetic poles. ing. The magnetic field 6 is provided between a cylindrical barrel 7 and a cylindrical inner tube 9 inserted into the barrel 7 together with a back yoke 8 formed of a cylindrical magnetic material attached to the outer periphery. It is housed within the annular gap.

The barrel 7 is formed of a non-magnetic material, and has a threaded portion 7a provided on the inner periphery of the left open end in FIG. 1 and a threaded portion 7b provided on the outer periphery of the right open end in FIG. I have. A bottom cap 12 is screwed onto the outer periphery of the right open end of the barrel 7 in FIG. 1 to close the right open end of the barrel 7 in FIG. The bottom cap 12 has a bottomed tubular shape including a bottom portion 12a and a tubular portion 12b, and is attached to the barrel 7 by screwing the tubular portion 12b onto the outer circumference of the barrel 7. A bracket 12c is provided on the cylindrical portion 12b of the bottom cap 12 so that the cylindrical linear motor 1 can be attached to equipment. The bottom cap 12 has a bottom portion 12a facing the right end 6b in FIG. 1, which is the other end of the magnetic field 6, and functions as a bottom member.

The inner tube 9 is formed of a non-magnetic material, and includes an annular head portion 9a that is attached to the open end on the left end of the barrel 7 in FIG. and a cylindrical portion 9b extending from the inner circumference of the right end in FIG. 1 of the head portion 9a of the inner tube 9 functions as a head member facing the left end 6a in FIG.

In addition, the inner tube 9 has a curved surface 9c at the boundary between the right end of the head portion 9a in FIG. 1 and the cylinder portion 9b. Stress is not concentrated on the boundary. In order to avoid such stress concentration, a tapered surface may be provided at the boundary between the head portion 9a and the cylindrical portion 9b.

The magnetic field 6 includes a plurality of annular permanent magnets 10a serving as main magnetic poles and a plurality of annular permanent magnets 10b serving as secondary magnetic poles, which are alternately stacked and inserted in the inner circumference of a cylindrical back yoke 8 in the axial direction. is configured with The permanent magnets 10a and 10b are laminated with an adhesive interposed therebetween in order to prevent scattering. In FIG. 1, the triangular marks on the permanent magnet 10a of the main pole and the permanent magnet 10b of the subsidiary pole indicate the magnetization direction, and the magnetization direction of the permanent magnet 10a of the main pole is the radial direction. , and the magnetization direction of the permanent magnet 10b of the secondary magnetic pole is the axial direction. The main magnetic pole permanent magnet 10a and the auxiliary magnetic pole permanent magnet 10b are arranged in a Halbach array. .

Further, in the cylindrical linear motor 1 of the present embodiment, the axial length of the main magnetic pole permanent magnet 10a is longer than the axial length of the auxiliary magnetic pole permanent magnet 10b. Thus, if the axial length of the permanent magnet 10a of the main magnetic pole is increased, the magnetic resistance between it and the permanent magnet 10a of the main magnetic pole can be reduced, and the magnetic field acting on the core 3 can be increased. The thrust of the cylindrical linear motor 1 can be improved.

Further, in the cylindrical linear motor 1 of the present embodiment, a back yoke 8 is provided around the outer peripheries of the permanent magnets 10a and 10b. By providing the back yoke 8, it is possible to secure a magnetic path with low magnetic resistance, thereby suppressing an increase in magnetic resistance caused by shortening the axial length of the permanent magnet 10b of the secondary magnetic pole. Therefore, if the axial length of the permanent magnet 10a of the main magnetic pole is made longer than the axial length of the permanent magnet 10b of the auxiliary magnetic pole, and a tubular back yoke 8 is provided on the outer circumference of the permanent magnets 10a and 10b, then the tubular linear motor 1 thrust can be greatly improved. The thickness of the back yoke 8 may be set to a thickness suitable for suppressing an increase in the external magnetic resistance of the permanent magnet 10a of the main magnetic pole.

An armature 2 is inserted axially movably on the inner peripheral side of the field magnet 6 , and the field magnet 6 applies a magnetic field to the core 3 . Since the magnetic field system 6 may apply a magnetic field to the movable range of the core 3, the installation range of the permanent magnets 10a and 10b may be determined according to the movable range of the core 3. FIG. Therefore, the permanent magnets 10a and 10b do not need to be installed in the range of the annular gap between the barrel 7 and the cylindrical portion 9b that cannot face the core 3.

In the present embodiment, the magnetic field 6 is composed of permanent magnets 10a and 10b arranged in a Halbach array. It may be configured by sequentially laminating an annular permanent magnet that is magnetized and has an S pole on the inner circumference.

Between the outer circumference of the cylindrical portion 9b and the inner circumference of the barrel 7, an annular head-side spacer 40, a field magnet 6, and an annular end-side spacer 41 are accommodated. The head-side spacer 40 has a tubular shape, and has a shape in which the outer diameter on the anti-field side, which is on the left side in FIG. 1, is larger than the outer diameter on the field side, which is on the right side in FIG. The left end of the large diameter portion 40a in FIG. 1 contacts the right end surface of the head portion 9a of the inner tube 9 in FIG. is in contact with the left end 6a of the .

Further, the inner circumference of the end face 40c of the large-diameter portion 40a of the head-side spacer 40 on the anti-field side end is chamfered to avoid the curved surface 9c of the inner tube 9, and a relief portion 40d is provided. By providing the head-side spacer 40 with the relief portion 40d in this way, the opposite-field-side end of the large-diameter portion 40a of the head-side spacer 40, which is the left end in FIG. can be abutted. Furthermore, the outer diameter of the small-diameter portion 40b is smaller than the inner diameter of the back yoke 8, and the small-diameter portion 40b enters the gap between the cylindrical portion 9b and the back yoke 8 to reach the left end 6a of the magnetic field 6. They are in direct contact.

The end-side spacer 41 is cylindrical, and has a shape in which the outer diameter on the anti-field side on the right side in FIG. 1 is larger than the outer diameter on the field side on the left side in FIG. The right end of the large diameter portion 41a in FIG. 1 abuts the left end surface of the bottom portion 12a of the bottom cap 12 in FIG. It abuts on the right end 6b. Furthermore, the outer diameter of the small diameter portion 41b is smaller than the inner diameter of the back yoke 8, and the small diameter portion 41b enters the gap between the cylindrical portion 9b and the back yoke 8 to reach the right end 6b of the magnetic field 6. They are in direct contact.

An annular recess 41c is provided at the end of the large-diameter portion 41a of the end-side spacer 41 on the antifield side, and an annular O-ring 42 is inserted into the recess 41c. The volume of the O-ring 42 is larger than the volume of the recess 41c when the O-ring 42 is not subjected to any external load.

1, an annular head-side spacer 40, a magnetic field 6, and an annular end-side spacer 41 are fitted in order from the left in FIG. After fastening, when the bottom cap 12 is attached to the right end of the barrel 7 in FIG. , and the magnetic field 6 is fixed to the inner circumference of the barrel 7 . The back yoke 8 attached to the outer periphery of the field system 6 is not axially sandwiched between the head portion 9a and the bottom cap 12, but is adhered to the field system 6 and does not move within the barrel 7. If the magnetic force of the field system 6 can restrain the movement of the back yoke 8 in the axial direction with respect to the field system 6 , the back yoke 8 may not be adhered to the field system 6 .

In this way, in a state where the magnetic field system 6 is fixed to the barrel 7, the cylindrical linear motor 1 does not generate thrust, and no reaction force is applied to the magnetic field system 6 in the axial direction due to the generation of the thrust force, the magnetic field system 6 and the left end of the end-side spacer 41 are in contact, and the right end of the end-side spacer 41 and the bottom portion 12a of the bottom cap 12 are in contact. In this state, the right end of the head-side spacer 40 contacts the left end 6 a of the magnetic field 6 , and the left end of the head-side spacer 40 contacts the left end of the head portion 9 a of the inner tube 9 . Furthermore, the O-ring 42 accommodated in the recess 41c of the end-side spacer 41 is pushed into the recess 41c in a compressed state by being pressed by the bottom 12a due to the contact between the right end of the end-side spacer 41 and the bottom 12a. and urges the end-side spacer 41 toward the magnetic field 6 side in the axial direction.

An annular seal member 28 is provided on the inner circumference of the head portion 9a and is in sliding contact with the outer circumference of the cover 17 that covers the outer circumference of the first rod 20. Intrusion is prevented.

A rod 11 on which the armature 2 is mounted is inserted into the inner tube 9 so as to be axially movable. Guided movement.

The cylindrical portion 9b forms a gap between the outer circumference of the core 3 and the inner circumferences of the permanent magnets 10a and 10b, and cooperates with the sliders 21b and 25 to guide the axial movement of the core 3. there is In the present embodiment, the armature 2 has only a single core 3. However, in the case of having a plurality of cores 3, not only the axial ends of the armature 2 but also the cores 3, 3 may be provided with a slider that slides on the inner circumference of the cylindrical portion 9b.

Further, a guide rod 16 is attached to the inner periphery of the bottom portion 12a of the bottom cap 12. As shown in FIG. The guide rod 16 includes a base end portion 16a fixed to the inner circumference of the bottom portion 12a, and a guide portion 16b extending from the base end portion 16a toward the rod 11 side and slidably inserted into the rod 11. , is always in sliding contact with the inner circumference of the rod 11 even when the cylindrical linear motor 1 expands and contracts. More specifically, the guide portion 16b of the guide rod 16 is slidably inserted toward the distal end side of the large inner diameter portion 21d of the second rod 21 .

As described above, in the cylindrical linear motor 1 of this embodiment, the guide rod 16 is in sliding contact with the inner circumference of the rod 11, and the sliders 21b and 25 are in sliding contact with the cylindrical portion 9b. It can move smoothly in the axial direction without eccentricity with respect to the magnetic field 6. - 特許庁

Further, in the tubular linear motor 1 constructed as described above, the tubular portion 9b, which guides the axial movement of the armature 2 and prevents the eccentricity of the armature 2 with respect to the magnetic field 6, is integrated with the head portion 9a. Therefore, the cylinder portion 9b and the head portion 9a are less likely to be distorted, and the sliders 21b and 25 can smoothly slide on the inner circumference of the cylinder portion 9b, and can be expanded and contracted smoothly.

The cylindrical linear motor 1 detects the position of the rod 11 with respect to the magnetic field 6 by a stroke sensor (not shown), grasps the electrical angle of the core 3 with respect to the magnetic field 6, switches the energization phase, and controls each winding by PWM control. It is driven by a controller that controls the amount of current in line 5 to control the thrust in cylindrical linear motor 1 and the moving direction of armature 2 . In addition, the control method in the controller described above is an example and is not limited to this. In addition, when an external force acts to relatively displace the armature 2 and the magnetic field 6 in the axial direction, the energization of the winding 5 or the induced electromotive force generated in the winding 5 produces a thrust that suppresses the relative displacement. can be generated to cause the cylindrical linear motor 1 to damp vibrations and motions of the equipment due to the external force, and energy regeneration to generate electric power from the external force is also possible.

As described above, the cylindrical linear motor 1 of the present invention has a plurality of annular permanent magnets 10a and 10b stacked such that the N poles and S poles are alternately arranged on the inner periphery in the axial direction. a magnetic field 6, an armature 2 axially movably inserted into the inner circumference of the magnetic field 6, a cylindrical barrel 7 covering the outer circumference of the magnetic field 6, and one opening of the barrel 7 A head portion (head member) 9a attached to the end and facing the left end (one end) 6a of the field 6, and a right end (the other end) of the field 6 attached to the other open end of the barrel 7. ) 6b, an annular end-side spacer (spacer) 41 interposed between the bottom cap (bottom member) 12 and the field magnet 6, and an end-side spacer (spacer) and an O-ring (elastic body) 42 that is housed in a concave portion 41c provided at the axial end of the magnetic field 41 and biases the magnetic field 6. As shown in FIG.

In the cylindrical linear motor 1 configured as described above, the magnetic field 6 is urged by the O-ring (elastic body) 42 accommodated in the concave portion 41c of the end-side spacer (spacer) 41. Even if the axial length of the magnetic field 6 changes slightly due to exposure to high heat due to long-term use of the motor 1, the O-ring (elastic body) 42 prevents the magnetic field 6 from wobbling in the barrel 7 in the axial direction. can be prevented. Further, since the O-ring (elastic body) 42 is accommodated in the concave portion 41c of the end-side spacer (spacer) 41 facing the magnetic field 6, the magnetic field 6 is Even if the reaction force of the thrust is received, not only the O-ring (elastic body) 42 but also the end-side spacer (spacer) 41 receives the reaction force. Axial deviation of the field 6 with respect to the barrel 7 can be suppressed without crushing the field 42 .

As described above, according to the cylindrical linear motor 1 configured as described above, it is possible to generate a high thrust force and prevent the magnetic field 6 from rattling.

In the above description, the O-ring 42 is used as the elastic body, but a spring washer, other springs, rubber, or the like may be used in addition to the O-ring 42, as long as the magnetic field 6 can be biased. good. Further, although the recess 41c does not necessarily have to be annular, if the recess 41c is formed in an annular shape and the elastic body is also annular, the urging force of the elastic body is applied to the cylindrical magnetic field 6 in the circumferential direction. , the axial rattling of the magnetic field 6 can be effectively suppressed.

Furthermore, in this embodiment, only the end-side spacer 41 is provided with the recess 41c and the O-ring (elastic body) is accommodated in the recess 41c. Alternatively, a recess may be provided in the head-side spacer 40, and an elastic body for biasing the magnetic field 6 in the axial direction may be accommodated in the recess of the head-side spacer.

In the present embodiment, the recess 41c provided in the end-side spacer (spacer) 41 has a structure having sidewalls on the inner and outer peripheries. The side spacer (spacer) 41 has a structure capable of receiving a reaction force due to the inner wall thickness and the outer peripheral wall thickness of the recess 41c, which is advantageous in terms of strength. A structure without side walls can also be adopted.

Further, in the present embodiment, since the recess 41c for accommodating the O-ring (elastic body) 42 is provided at the end of the end-side spacer (spacer) 41 on the anti-field side, maintenance of the cylindrical linear motor 1 is facilitated. If the bottom cap (bottom member) 12 is removed from the barrel 7, the O-ring (elastic body) 42 can be accessed without removing the end side spacer (spacer) 41 from the barrel 7, and the O-ring (elastic body) 42 can be replaced. easier. In the tubular linear motor 1 of the present embodiment, the tubular portion 9b of the inner tube 9 is integrated with the head portion 9a as a head member. It may be detachable, in which case the head side spacer 40 can be used as a spacer, provided with a recess on the opposite side of the magnetic field, and an elastic body can be accommodated in the recess to form a head portion. Since the elastic body can be easily replaced by removing 9a, it may be done in this manner.

A recess may be provided at the end of the end-side spacer 41 on the field side to accommodate an O-ring, or a recess may be provided at the end of the head-side spacer 40 on the field side to accommodate the O-ring. Otherwise, the O-ring will seize on the magnetic field 6 exposed to high temperatures due to the use of the cylindrical linear motor 1, making it difficult to replace the O-ring. However, when using an elastic body that does not need to be replaced, a recess may be provided at the end of the end-side spacer 41 on the field side and the elastic body may be accommodated in the recess. A concave portion may be provided at the end of the elastic body to accommodate the elastic body.

Further, in the cylindrical linear motor 1 of the present embodiment, the axial ends of the end-side spacers (spacers) 41 are in a no-load state where the armature 2 is not energized and the magnetic field 6 is in contact with the O-ring. The bottom cap (bottom member) 12 and the magnetic field 6 are in contact with each other when the armature 2 receives no axial load other than the elastic force of the armature 2, that is, when the armature 2 is in a no-load state. ing. In the cylindrical linear motor 1 configured as described above, the axial end of the end-side spacer (spacer) 41 is in contact with the bottom cap (bottom member) 12 and the magnetic field 6 when the armature 2 is in a no-load state. Since they are in contact with each other, the field magnet 6 is supported by the end-side spacer (spacer) 41 even if a reaction force acts on the field magnet 6 when the thrust force is generated. As a result, axial displacement of the field 6 with respect to the barrel 7 can be effectively prevented. When the head-side spacer 40 is used as a spacer and a concave portion is provided in the head-side spacer 40 to house the elastic body in the concave portion, the axial end portion of the head-side spacer 40 is pushed when the armature 2 is in a no-load state. If the head portion (head member) 9a and the magnetic field 6 are brought into contact with each other, it is possible to effectively prevent the magnetic field 6 from being axially displaced from the barrel 7 when a reaction force acts on the magnetic field 6 when a thrust force is generated. can.

Furthermore, in the cylindrical linear motor 1 of the present embodiment, the concave portion 41c is an annular concave portion, and the elastic body is the annular O-ring 42 . According to the cylindrical linear motor 1 configured in this manner, the standardized and compact O-ring 42 is made of an elastic body, so that the O-ring 42 can be easily attached to the end-side spacer (spacer) 41. In addition, since the O-ring 42 is inexpensive and readily available, the cylindrical linear motor 1 can be manufactured at low cost. When the O-ring 42 is used as the elastic body, it is preferable to provide a concave portion 41c at the anti-field side end of the end-side spacer (spacer) 41 in view of ease of replacement during maintenance. Also, if only the head portion 9a can be removed from the barrel 7, even if a recess for accommodating the O-ring 42 is provided at the anti-field side end of the head-side spacer 40, replacement at the time of maintenance is similarly possible. easier.

Further, in this embodiment, even if an axial force acts on the head portion 9a of the inner tube 9 as a reaction force when the armature 2 is driven in the axial direction, the boundary between the head portion 9a and the cylindrical portion 9b is curved. Since the surface 9c is provided, stress concentration on the boundary portion of the inner tube 9 can be alleviated. Since the head-side spacer 40 is provided with the relief portion 40d that avoids the curved surface 9c, the end surface 40c of the head-side spacer 40 can directly face the head portion 9a and contact the head portion 9a. The contact pressure between the head-side spacer 40 and the head portion 9a due to the axial force can be reduced.

Although preferred embodiments of the invention have been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 1... Cylindrical linear motor 2... Armature 6... Field magnet 7... Barrel 9a... Head part (head member) 10a, 10b... Permanent magnet 12 ... bottom cap (bottom member), 41 ... end-side spacer (spacer), 41c ... concave portion, 42 ... O-ring (elastic body)

Claims (3)

a tubular magnetic field magnet having a plurality of annular permanent magnets stacked such that N poles and S poles are alternately arranged on the inner periphery in the axial direction;
an armature inserted axially movably on the inner peripheral side of the magnetic field;
a cylindrical barrel covering the outer periphery of the magnetic field;
a head member attached to one open end of the barrel and facing one end of the field;
a bottom member attached to the other open end of the barrel and facing the other end of the field;
an annular spacer interposed between at least one of the head member and the bottom member and the field magnet;
A cylindrical linear motor, comprising: an elastic body that is accommodated in a recess provided in an axial end of the spacer and biases the magnetic field. 2. The tubular linear motor according to claim 1, wherein the concave portion is provided at the end of the spacer on the anti-field side. 3. The cylindrical linear motor according to claim 1, wherein the spacer is in contact with one of the head member and the bottom member and the magnetic field when the armature is in a no-load state. .