JP7569534B2 - Cylindrical Linear Motor - Google Patents

Description

The present invention relates to a cylindrical linear motor.

A cylindrical linear motor has a cylindrical field magnet and an armature inserted into the field magnet so that it can move axially. The armature has a ring-shaped core with multiple ring-shaped teeth on its outer periphery, and windings that are fitted into slots between the teeth. In a cylindrical linear motor configured in this way, the field magnet can be driven axially relative to the armature by passing current through the armature windings.

In a cylindrical linear motor, the driving direction of the field magnet is the axial direction, so the core in the armature has ends in the axial direction, and cogging thrust is generated due to the end effect of the core.

In order to reduce the cogging thrust caused by the end effect of such cores, a cylindrical linear motor has been proposed in which the armature is made up of two axially arranged cores and a non-magnetic spacer interposed between the cores. In a cylindrical linear motor configured in this way, the cores are spaced at an appropriate distance by the spacer, so that the cogging thrust caused by the end effect of one core is cancelled out by the cogging thrust caused by the end effect of the other core, thereby reducing the cogging thrust overall (see, for example, Patent Document 1).

Separately, a cylindrical linear motor has been proposed in which one armature group is made up of three armatures arranged with an electrical angle of 120 degrees, and the three armatures groups are arranged with an electrical angle of 60 degrees, with interpoles made of soft iron or silicon steel inserted between the armature groups (see, for example, Patent Document 2). In the cylindrical linear motor of Patent Document 2, the interpoles between the armature groups reduce the end effect in the armature groups.

International Publication No. 2019/202758 JP 2019-22412 A

In the cylindrical linear motor disclosed in Patent Document 1, multiple cores are arranged at appropriate intervals in the axial direction to cancel out the cogging thrust of one core with the cogging thrust of the other core. However, since there are two ends per core, and end effects occur at a total of four ends, it is desirable to further reduce the cogging thrust.

In addition, in the cylindrical linear motor disclosed in Patent Document 2, the spacing between the armature blocks is half the slot pitch, which corresponds to an electrical angle of 60 degrees, so there is a problem in that thrust is reduced due to a misalignment between the magnet pitch of the field magnet and the slot pitch in the armature. In addition, because three armatures are arranged side by side with gaps between them in each armature group, end effects occur at the two ends of each armature, so it is desirable to further reduce the cogging thrust.

The present invention aims to provide a cylindrical linear motor that can reduce cogging thrust while improving thrust.

To achieve the above object, the cylindrical linear motor of the present invention comprises a cylindrical field magnet, a plurality of cylindrical cores arranged in the axial direction, each having a plurality of teeth spaced apart in the axial direction around the field magnet side, and arranged on the inner or outer circumference of the field magnet so as to be movable in the axial direction relative to the field magnet, a winding attached to the slot between the teeth of the core, and an annular spacer made of a magnetic material interposed between the cores, and an armature having the axial width of the spacer set to an integer multiple of the slot pitch, which is the pitch of the slots.

In a cylindrical linear motor configured in this manner, the spacers interposed between the multiple cores that make up the armature are made of a magnetic material, so the ends of the cores on the spacer side do not produce end effects. In addition, the axial width of the spacer is an integer multiple of the slot pitch in the core, so there is no misalignment between the magnet pitch of the field magnet and the slot pitch of the core, which does not lead to a decrease in thrust and allows the windings of the multiple cores to be driven by a single drive circuit.

In addition, the spacer in the cylindrical linear motor may have recesses at both ends in the axial direction. If the spacer has recesses in this way, the spacer becomes lighter, so the entire mass of the cylindrical linear motor becomes lighter, and the mass thrust density of the cylindrical linear motor is improved. Furthermore, the cylindrical linear motor may have a pair of sliders arranged at both ends in the axial direction of the armature, the field magnet has a non-magnetic tube on the armature side, and the spacer and slider have a wear ring that slides against the circumferential surface of the tube around the field magnet side. According to the cylindrical linear motor configured in this way, the armature having multiple cores is supported at at least three points by the spacers and sliders, so that the armature can move smoothly in the axial direction without being eccentric with respect to the field magnet.

The cylindrical linear motor of the present invention can improve thrust while reducing cogging thrust.

1 is a vertical cross-sectional view of a cylindrical linear motor according to an embodiment;

The present invention will be described below based on the embodiment shown in the drawings. As shown in FIG. 1, the cylindrical linear motor 1 in one embodiment is configured with a cylindrical field magnet 6, two cylindrical cores 3, 3 arranged side by side in the axial direction, each of which is arranged on the inner periphery of the field magnet 6 so as to be movable in the axial direction relative to the field magnet 6 and has a plurality of teeth 3b spaced apart in the axial direction on the outer periphery surrounding the field magnet side, a winding 4 attached to the slot 3c between the teeth 3b, 3b of the core 3, and an annular spacer 5 made of a magnetic material interposed between the cores 3, 3.

The components of the cylindrical linear motor 1 will be described in detail below. The armature 2 includes a core 3, a winding 4 attached to slots 3c between the teeth 3b, 3b of the core 3, and a spacer 5 provided between the cores 3, 3, and is attached to the outer periphery of a cylindrical rod 11. The armature 2 thus configured is inserted into the cylindrical field magnet 6 so as to be movable in the axial direction, and can move axially relative to the field magnet 6, and in this embodiment serves as a stator.

The cores 3, 3 are both of the same shape, and are comprised of a cylindrical core body 3a and a number of annular teeth 3b provided on the outer periphery of the core body 3a, and are attached to the outer periphery of the rod 11 in a line in the axial direction.

As mentioned above, the core body 3a is cylindrical, and its thickness is ensured so that the cross-sectional area is equal to or greater than the cross-sectional area of the teeth 3b when cut anywhere from the inner periphery to the outer periphery with a cylinder centered on the axis of the core 3.

In this embodiment, as shown in FIG. 1, ten teeth 3b are arranged at equal intervals in the axial direction on the outer periphery of the core body 3, and slots 3c are formed between the teeth 3b, each of which is a gap into which a winding 4 is attached. In this embodiment, the teeth 3b have a trapezoidal cross-sectional shape with a larger width at the inner periphery than at the outer periphery to ensure a large magnetic path cross-sectional area on the inner periphery side, but they may also have a rectangular cross-sectional shape with the same axial length (width) from the inner periphery to the outer periphery.

In addition, in this embodiment, a total of nine slots 3c consisting of gaps are provided between adjacent teeth 3b, 3b in FIG. 1. Windings 4 are wound and attached to these slots 3c. The windings 4 are three-phase windings of U-phase, V-phase, and W-phase. The nine slots 3c of the core 3 on the left side in FIG. 1 are fitted with windings 4 of W-phase, W-phase, W-phase and U-phase, U-phase, U-phase, U-phase and V-phase, V-phase, V-phase, and V-phase and W-phase from the left side in FIG. 1. The nine slots 3c of the core 3 on the right side in FIG. 1 are fitted with windings 4 of W-phase and U-phase, U-phase, U-phase, U-phase and V-phase, V-phase, V-phase and W-phase, W-phase, and W-phase from the left side in FIG. 1. Note that the phases of the windings 4 that are attached to the slots 3c of each core 3 are just an example and are not limited to this, and can be changed as appropriate depending on the number of poles and the number of slots.

The cores 3, 3 thus constructed are mounted on the outer periphery of the rod 11, which is the output shaft and is made of a non-magnetic material. Specifically, the cores 3, 3 are fitted to the outer periphery of the tip side of the rod 11, which is the right end side in FIG. 1, and are fixed to the rod 11 by being sandwiched between a pair of annular sliders 12, 13 made of a non-magnetic material and attached to the rod 11. Wear rings 12a, 13a are attached to the outer periphery of the sliders 12, 13. In addition, a spacer 5 made of a magnetic material that is fitted to the outer periphery of the rod 11 together with the cores 3, 3 is interposed between the cores 3, 3, and the cores 3 and 3 are fixed to the rod 11 with a gap of the axial length L1 of the spacer 5. The outer diameters of the sliders 12, 13 and the spacer 5 are set to be larger than the outer diameters of the cores 3, 3.

The spacer 5 is formed of an annular magnetic material, and has annular recesses 5a, 5b at both ends in the axial direction, and a wear ring 5c is attached to the outer periphery. In this way, the spacer 5 has the recesses 5a, 5b and is hollowed out, so it is lighter than a simple annular spacer without the recesses 5a, 5b. The axial width L1 of the spacer 5 is set to twice the length of the slot pitch L2 of the core 3. The axial width L1 of the spacer 5 only needs to satisfy L1 = n x L2, where n is an integer. In other words, the axial width L1 of the spacer 5 only needs to be set to an integer multiple of the slot pitch L2 of the core 3.

The rod 11 holding the armature 2 is inserted into the field magnet 6 so as to be freely movable in the axial direction. The left end of the rod 11 in FIG. 1 protrudes outward from the barrel 7 through an annular head cap 15 attached to the left end in FIG. 1 of the barrel 7 that covers the outer periphery of the field magnet 6. A bracket 16 is attached to the base end side of the rod 11, which is the left end in FIG. 1, to enable attachment to equipment, etc. in which the cylindrical linear motor 1 is installed.

The windings 4 of the same phase mounted in the slots 3c of each core 3 are connected in series by a jumper wire (not shown), and the windings 4 at one end of each phase connected in series are connected to each other on the spacer side of the core 3. The connection parts 4a where the windings 4 of each core 3 are connected to each other are housed in the recesses 5a and 5b of the spacer 5. In this way, the recesses 5a and 5b in the spacer 5 not only contribute to reducing the weight of the spacer 5, but also function as a housing part for housing the connection parts 4a that connect the windings 4 to each other. Furthermore, the lead wires 17 drawn from the windings 4 at the other end of each phase connected in series are drawn out from the base end side of the rod 11, which is the left end in FIG. 1, through the annular gap between the rod 11 and the cylindrical cover 14 that covers the outer periphery of the rod 11, to the outside of the cylindrical linear motor 1 and connected to a power source via a drive circuit such as an inverter (not shown). In the cylindrical linear motor 1 of this embodiment, the armature 2 functions as a stator.

On the other hand, in this embodiment, the field magnet 6 is composed of an annular main pole permanent magnet 6a and an annular sub pole permanent magnet 6b that are alternately stacked and inserted in the axial direction, and a cylindrical back yoke 8 made of a magnetic material that is fitted onto the outer periphery of the permanent magnets 6a and 6b.

The field magnet 6 is housed in an annular gap formed between the barrel 7, which is made of a cylindrical non-magnetic material, and the cylindrical inner tube 9, which is inserted into the barrel 7, and in this embodiment, functions as a mover. Therefore, the mover of the cylindrical linear motor 1 in this embodiment is composed of the field magnet 6, the barrel 7, and the inner tube 9.

In addition, the triangular marks on the main pole permanent magnet 6a and the sub pole permanent magnet 6b in FIG. 1 indicate the magnetization direction, with the main pole permanent magnet 6a being magnetized in the radial direction and the sub pole permanent magnet 6b being magnetized in the axial direction. The main pole permanent magnets 6a and the sub pole permanent magnets 6b are alternately stacked, and the magnetic pole arrangement of adjacent main pole permanent magnets 6a and adjacent sub pole permanent magnets 6b is arranged so that they are in the opposite direction to each other, forming a magnet array M in a so-called Halbach array. The permanent magnets 6a and 6b are arranged on the inner periphery of the field magnet 6 so that the south and north poles appear alternately in the axial direction.

The axial length of the main pole permanent magnet 6a is longer than the axial length of the sub pole permanent magnet 6b, and in this embodiment, is set to be in the range of two to five times the axial length of the sub pole permanent magnet 6b. By setting the axial length of the main pole permanent magnet 6a within the above-mentioned range, the magnetic resistance between the main pole permanent magnet 6a and the cores 3, 3 can be reduced, and the magnetic field acting on the cores 3, 3 can be increased, thereby improving the thrust of the cylindrical linear motor 1.

In addition, in the cylindrical linear motor 1 of the present invention, a back yoke 8 is provided on the outer periphery of the magnet array M formed by the permanent magnets 6a and 6b. By providing the back yoke 8, a magnetic path with low magnetic resistance can be secured even if the axial length of the permanent magnet 6b of the sub-pole is shortened, so that the thrust of the cylindrical linear motor 1 can be effectively improved when the axial length of the permanent magnet 6a of the main pole is lengthened. More specifically, by providing the back yoke 8 on the outer periphery of the permanent magnets 6a and 6b, a magnetic path with low magnetic resistance can be secured, so that an increase in magnetic resistance can be suppressed even if the axial length of the permanent magnet 6b of the sub-pole is shortened. Therefore, by making the axial length of the permanent magnet 6a of the main pole longer than the axial length of the permanent magnet 6b of the sub-pole and providing a cylindrical back yoke 8 on the outer periphery of the permanent magnets 6a and 6b, the thrust of the cylindrical linear motor 1 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 6a of the main pole. Although providing a back yoke 8 can suppress an increase in magnetic resistance, the back yoke 8 can also be omitted.

The permanent magnet 6b of the sub-pole is a permanent magnet with a higher coercive force than the permanent magnet 6a of the main pole. The residual magnetic flux density and coercive force of a permanent magnet are closely related to each other, and generally, increasing the residual magnetic flux density reduces the coercive force, and increasing the coercive force reduces the residual magnetic flux density, so that they are in a mutually contradictory relationship. In the Halbach arrangement, a strong magnetic field is applied to the permanent magnet 6b of the sub-pole in the demagnetization direction, so the coercive force of the permanent magnet 6b of the sub-pole is increased to suppress demagnetization and allow a strong magnetic field to act on the cores 3, 3. On the other hand, the strength of the magnetic field acting on the cores 3, 3 depends on the number of magnetic field lines of the permanent magnet 6a of the main pole. Therefore, a permanent magnet with a high residual magnetic flux density is used for the permanent magnet 6a of the main pole to allow a strong magnetic field to act on the cores 3, 3. In this embodiment, in order to make the permanent magnet 6b of the sub-pole higher in coercivity than the permanent magnet 6a of the main pole, the material of the permanent magnet 6b of the sub-pole is made of a material with a higher coercivity than the material of the permanent magnet 6a of the main pole. Therefore, by selecting the material, the combination of the permanent magnet 6a of the main pole and the permanent magnet 6b of the sub-pole can be easily realized. In this embodiment, the permanent magnet 6a of the main pole is made of a material with a high residual magnetic flux density, mainly composed of neodymium, iron, and boron, and the permanent magnet 6b of the sub-pole is made of a magnet that is difficult to demagnetize, with the addition of heavy rare earth elements such as dysprosium and terbium to the above material.

As described above, the field magnet 6 has a configuration in which the permanent magnets 6a, 6b are stacked in a Halbach array to apply a stronger magnetic field to the armature 2, but as long as the permanent magnets are stacked so that S and N poles appear alternately in the axial direction on the armature 2 side and a magnetic field can be applied to the armature 2, the field magnet 6 may be composed of multiple permanent magnets stacked in an array other than the Halbach array.

Next, the inner tube 9 is cylindrical and made of a non-magnetic material, and is fitted to the inner circumference of the field magnet 6. Furthermore, a head cap 15, whose annular inner diameter is smaller than that of the inner tube 9 and whose outer diameter is larger than that of the inner tube 9, is integrally provided at the left end of the inner tube 9 in FIG. 1. The wear rings 5c, 12a, and 13a of the spacer 5 and the sliders 12 and 13 are in sliding contact with the inner circumference of the inner tube 9, and the armature 2 can move smoothly in the axial direction together with the rod 11 without being eccentric with respect to the field magnet 6 by being supported at three points by the spacer 5 and the sliders 12 and 13. The inner tube 9 forms an annular gap between the outer circumference of the core 3 and the inner circumference of the field magnet 6, and plays a role in guiding the axial movement of the armature 2 in cooperation with the sliders 12 and 13 and the spacer 5. The inner tube 9 may be made of a non-magnetic material, but if it is made of synthetic resin, the mass thrust density of the cylindrical linear motor 1 is improved. The mass thrust density is an index of the performance of the cylindrical linear motor 1, and the higher the value, the more efficiently the thrust can be generated. The inner tube 9 also prevents the core 3 from adhering to the field magnet 6 when the armature 2 is inserted into the field magnet 6, which allows for good assembly. Thus, although there are many advantages to providing the inner tube 9, it is also possible to omit the inner tube 9.

The inner tube 9 may be made of a non-magnetic metal, but if it is a non-magnetic metal, eddy currents will be generated inside the inner tube 9 when the armature 2 moves in the axial direction, generating a force that hinders the movement of the armature 2. In contrast, if the inner tube 9 is made of a synthetic resin, no eddy currents will be generated, so the thrust of the cylindrical linear motor 1 can be improved more effectively and the mass of the cylindrical linear motor 1 can be reduced. If the inner tube 9 is made of a synthetic resin, it can be made of fluororesin to reduce friction and wear between the sliders 12, 13 and the spacer 5. The inner tube 9 may also be made of other synthetic resins, and the inner circumference of the inner tube 9 made of other synthetic resins may be coated with fluororesin to reduce friction and wear.

The barrel 7 is made of a non-magnetic material and is formed into a cylindrical shape with a bottom, and the magnetic force of the field magnet 6 prevents the adhesion of contaminants such as iron sand to the outer periphery of the barrel 7. The right end of the barrel 7 and the inner tube 9 in FIG. 1 is closed by the bottom 7a of the barrel 7, and the left end of the barrel 7 in FIG. 1 is closed by a head cap 15 that is provided at the left end of the inner tube 9 and screwed to the inner periphery of the barrel 7. The bottom 7a at the right end of the barrel 7 in FIG. 1 is equipped with a bracket 7b that can attach the cylindrical linear motor 1 to equipment, etc. The cylindrical linear motor 1 is used by being attached to equipment, etc. using a bracket 16 attached to the base end of the rod 11 on the stator side and a bracket 7b provided on the bottom 7a that closes the end of the barrel 7 on the movable side.

In this embodiment, the inner tube 9 and the head cap 15 are integrated and configured as one component, but the inner tube 9 and the head cap 15 may be configured as separate components. Furthermore, when fastening the barrel 7 and the head cap 15, other fastening methods such as fastening with bolts and nuts or welding may be used in addition to screw fastening. Also, the tubular portion and the bottom portion 7a of the barrel 7 may be separate components, and the tubular portion and the bottom portion 7a may be connected to each other.

The head cap 15 is equipped with a seal member 15a that seals around the axis of the cover 14 that covers the rod 11 inserted into the inner circumference, preventing dust, water, etc. from entering the cylindrical linear motor 1. The axial length of the barrel 7 and the inner tube 9 is longer than the combined axial length of the armature 2, the spacer 5, and the sliders 12 and 13, and the armature 2 can stroke left and right in FIG. 1 within the range of the axial length within the field magnet 6.

The magnet array M formed by stacking the permanent magnets 6a and 6b in the field magnet 6 is fixed to the barrel 7 by being sandwiched between the bottom 7a that closes the end of the barrel 7 and the head cap 15 that is screwed to the open end of the barrel 7. Specifically, annular retainers 18 and 19 are interposed between the left end of the magnet array M in FIG. 1 and the head cap 15, and between the right end of the magnet array M in FIG. 1 and the bottom 7a, respectively. The magnet array M is sandwiched between the head cap 15 and the bottom 7a via these retainers 18 and 19, and is fixed to the barrel 7 of the field magnet 6, and its axial position relative to the barrel 7 is adjusted. If the position of the field magnet 6 can be adjusted and fixed between the head cap 15 and the bottom 7a of the barrel 7, the retainers 18 and 19 can be omitted. The retainers 18 and 19 may also be formed by stacking multiple washers.

In the cylindrical linear motor 1, the armature 2 and the field 6 can move relative to each other in the axial direction, and the field 6, which is the mover, can be driven in the axial direction by energizing the windings 4 to provide thrust to the equipment. For example, by sensing the electrical angle of the field 6 relative to the windings 4 and switching the energizing phase based on the electrical angle while controlling the amount of current in each winding 4 by PWM control, the thrust in the cylindrical linear motor 1 and the direction of movement of the field 6, which is the mover, can be controlled. Note that the above-mentioned control method is one example and is not limited to this. Thus, in the cylindrical linear motor 1 of this embodiment, the armature 2 is the stator, and the field 6 behaves as the mover. In addition, when an external force acts to displace the armature 2 and the field magnet 6 relative to each other in the axial direction, a thrust force that suppresses the relative displacement can be generated by passing electricity through the windings 4 or by induced electromotive force generated in the windings 4, allowing the cylindrical linear motor 1 to damp the vibration and movement of the equipment caused by the external force, and energy regeneration that generates electricity from the external force is also possible.

As described above, the cylindrical linear motor 1 of this embodiment includes a cylindrical field magnet 6, a plurality of cylindrical cores 3 arranged in the axial direction, each having a plurality of teeth 3b spaced apart in the axial direction on the outer periphery of the field magnet 6, which are arranged on the inner periphery of the field magnet 6 so as to be movable in the axial direction relative to the field magnet 6, a winding 4 attached to the slots 3c between the teeth 3b, 3b of the cores 3, and an annular spacer 5 made of a magnetic material interposed between the cores 3, 3, and the axial width of the spacer 5 is set to an integer multiple of the slot pitch, which is the pitch of the slots 3c.

In the cylindrical linear motor 1 configured in this manner, the spacer 5 interposed between the multiple cores 3, 3 that make up the armature 2 is made of a magnetic material, so the ends of the cores 3, 3 on the spacer side do not produce an end effect. Therefore, according to the cylindrical linear motor 1 of this embodiment, the ends of the cores 3, 3 that produce an end effect on the armature 2 as a whole are only the two ends on the opposite side to the spacer, so the cogging thrust due to the end effect can be reduced.

If the axial width of the spacer 5 is set to a length other than an integer multiple of the slot pitch, the one core 3 and the other core 3 will face each other at different electrical angles relative to the field 6, which will not only reduce the thrust, but will also force the windings 4 of one core 3 and the windings 4 of the other core 3 to be energized at different times, requiring as many drive circuits as there are cores 3 to drive the cylindrical linear motor 1. In contrast, the axial width of the spacer 5 in the cylindrical linear motor 1 of this embodiment is an integer multiple of the slot pitch of the core 3, so there is no misalignment between the magnet pitch of the field 6 and the slot pitch of the core 3, and the thrust is not reduced, and the windings 4 of the two cores 3 can be driven by a single drive circuit.

As a result, the cylindrical linear motor 1 of this embodiment can improve thrust while reducing cogging thrust.

In the cylindrical linear motor 1 described above, the armature 2 is configured with two cores 3 and one spacer 5 interposed between the cores 3, 3. However, if the armature 2 has three or more cores 3, a spacer 5 having an axial width that is an integer multiple of the slot pitch may be interposed between each of the cores 3, 3. In general, in the case of an armature 2 having X cores 3, one spacer 5 may be provided between each of the (X-1) cores 3, 3, so that (X-1) spacers 5 may be provided. In addition, the axial width L1 of the spacer 5 may be set to a length n times the slot pitch L2 of the core 3, where n is an arbitrary integer. If the armature 2 has multiple spacers 5, the axial widths of the spacers 5 may not be equal. However, if the spacer 5 is light, the cylindrical linear motor 1 will also be light, and the mass thrust density of the cylindrical linear motor 1 will be improved, so it is preferable that the axial width L1 of all spacers 5 is equal to the slot pitch L2 of the core 3.

In addition, in the cylindrical linear motor 1 of this embodiment, a structure is adopted in which a cylindrical field magnet 6 is arranged on the outer periphery of the armature 2, but a structure may also be adopted in which teeth 3b are provided on the inner periphery of the core 3, slots 3c in which the windings 4 are attached are formed on the inner periphery of the core 3, and the field magnet 6 is inserted inside the armature 2. In this way, the cylindrical linear motor 1 includes a cylindrical field magnet 6, a plurality of cores 3 that are arranged in the axial direction and have a plurality of teeth 3b that are arranged on the inner or outer periphery of the field magnet 6 so as to be movable in the axial direction relative to the field magnet 6 and are arranged around the field magnet side at intervals in the axial direction, a winding 4 that is attached to the slots 3c between the teeth 3b, 3b of the core 3, and an annular spacer 5 formed of a magnetic material that is interposed between the cores 3, 3, and the axial width of the spacer 5 is set to an integer multiple of the slot pitch.

In addition, in the cylindrical linear motor 1 of this embodiment, the spacer 5 has recesses 5a and 5b at both ends in the axial direction. Since the spacer 5 has the recesses 5a and 5b in this way, the spacer 5 is lightweight, and the overall mass of the cylindrical linear motor 1 is also lightweight, and the mass thrust density of the cylindrical linear motor 1 can be improved. Furthermore, since the spacer 5 has the recesses 5a and 5b, the connection portion 4a of the winding 4 attached to the core 3 can be accommodated in the recesses 5a and 5b, protecting the connection portion 4a and preventing interference with other components. Note that the spacer 5 may have recesses only on one side instead of both axial sides, and the recesses 5a and 5b may not be annular and may not be continuous in the circumferential direction.

The cylindrical linear motor 1 of this embodiment is provided with a pair of sliders 12, 13 arranged at both ends of the armature 2 in the axial direction, a non-magnetic inner tube (tube) 9 on the inner periphery where the field magnet 6 is on the armature side, and the spacer 5 and the sliders 12, 13 are provided with wear rings 5c, 12a, 13a on the outer periphery that slide against the circumferential surface of the inner tube (tube) 9. According to the cylindrical linear motor 1 configured in this manner, the armature 2 having a plurality of cores 3, 3 is supported at three or more points by the spacer 5 and the sliders 12, 13, so that the armature 2 can move smoothly in the axial direction without being eccentric with respect to the field magnet 6. When the cylindrical linear motor 1 adopts a structure in which the armature 2 is arranged on the outer periphery side of the field magnet 6, a non-magnetic tube is provided on the outer periphery of the field magnet 6, and wear rings that slide against the outer periphery of the tube are provided on the inner periphery of the spacer and slider provided on the armature 2 side. In this case, the core, spacer, and slider are attached to the inner circumference of the non-magnetic barrel 7, and the field magnet and tube are attached to the outer circumference of the rod 11. In other words, with a cylindrical linear motor 1 in which a pair of sliders 12, 13 are arranged on both ends of the axial direction of the armature 2, the field magnet 6 has a non-magnetic tube on the armature side, and the spacer 5 and sliders 12, 13 have wear rings 5c, 12a, 13a that slide against the circumferential surface of the tube around the periphery of the field magnet side, the armature 2 can move smoothly in the axial direction without being eccentric relative to the field magnet 6.

In the cylindrical linear motor 1 of this embodiment, the spacer 5 is separate from the core 3, but it is also possible to adopt a configuration in which the spacer 5 is integrated into the core 3. For example, if a structure in which the spacer 5 is integrated into one end of the core 3 is used as a core unit, the armature 2 can be constructed by stacking one or more core units on one core 3 as many times as desired.

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

1: cylindrical linear motor, 2: armature, 3: core, 3b: teeth, 3c: slot, 4: winding, 5: spacer, 5a, 5b: recess, 5c, 12a, 13a: wear ring, 6: field magnet, 12, 13: slider

Claims (3)

A cylindrical field magnet,
a plurality of cores arranged in the axial direction, each core being cylindrical and having a plurality of teeth arranged at intervals in the axial direction around the periphery of the field magnet and axially movably disposed on the inner or outer periphery of the field magnet, a winding fitted in a slot between the teeth of the core, and an annular spacer made of a magnetic material interposed between the cores;
A cylindrical linear motor, characterized in that the axial width of the spacer is set to an integer multiple of a slot pitch, which is the pitch of the slots. 2. The cylindrical linear motor according to claim 1, wherein the spacer has a recess at one or both axial ends. a pair of sliders disposed at both ends of the armature in an axial direction,
The field magnet has a non-magnetic tube on the armature side,
3. The cylindrical linear motor according to claim 1, wherein the spacer and the slider have wear rings on the periphery on the field side that come into sliding contact with the circumferential surface of the tube.

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