Linear actuator, linear actuator manufacturing method, and shaft manufacturing method

Abstract

One embodiment of the present disclosure provides: a linear actuator of reduced weight that can be driven with high accuracy; a linear actuator manufacturing method; and a shaft manufacturing method. The linear actuator comprises: a cylindrical coil; and a shaft that passes through the inside of the coil. The shaft comprises a plurality of permanent magnets arranged with the same poles facing each other. The plurality of permanent magnets has gaps between adjacent permanent magnets, and the adjacent permanent magnets are bonded by an adhesive applied at the gaps.

Description

Linear actuator, method of manufacturing a linear actuator, and method of manufacturing a shaft

[0001] The present invention relates to a linear actuator, a method for manufacturing a linear actuator, and a method for manufacturing a shaft, and more particularly to a linear actuator having a cylindrical coil and a shaft that passes through the inside of the coil, a method for manufacturing a linear actuator, and a method for manufacturing a shaft.

[0002] A cylindrical linear motor is known as one type of linear actuator. A cylindrical linear motor consists of a shaft that generates alternating magnetic flux of north and south poles, and a cylindrical coil placed around the shaft. When a current is passed through the coil, the coil is driven linearly. A cylindrical linear motor is also called a shaft motor.

[0003] Patent document 1 describes a configuration of the shaft of a cylindrical linear motor in which multiple magnets are arranged in series with the same poles facing each other, and the magnets are housed in a pipe-shaped member with a gap between adjacent magnets.

[0004] Japanese Patent Application Laid-Open No. 2005-237165

[0005] One embodiment of the technique of the present disclosure provides a linear actuator that can be lightened and driven with high precision, a method for manufacturing the linear actuator, and a method for manufacturing a shaft.

[0006] (1) A linear actuator comprising a cylindrical coil and a shaft passing through the inside of the coil, the shaft including a plurality of permanent magnets arranged with like poles facing each other, the plurality of permanent magnets having gaps between adjacent permanent magnets, and the adjacent permanent magnets being bonded together with adhesive applied to the gaps.

[0007] (2) A linear actuator according to (1), wherein the shaft further includes a cylindrical member that houses a plurality of permanent magnets, and the cylindrical member has an opening on its outer surface corresponding to the position of the gap.

[0008] (3) The linear actuator according to (2), wherein the cylindrical member has a plurality of openings for one gap.

[0009] (4) A linear actuator according to (2) or (3), wherein the opening is configured as a slot extending along the axial direction of the shaft.

[0010] (5) A linear actuator described in (4), in which the width of the gap in the axial direction of the shaft is s and the width of the elongated hole in the circumferential direction of the tubular member is t, the gap and the elongated hole have a relationship of t > s.

[0011] (6) A linear actuator described in any one of (1) to (5), wherein the shaft further includes a spacer disposed between adjacent permanent magnets to form a gap, and the spacer has a retaining portion that retains adhesive between the spacer and the permanent magnet.

[0012] (7) A linear actuator according to (6), wherein the spacer has a hollow shape with both ends open, and the hollow portion constitutes a holding portion.

[0013] (8) A linear actuator according to (7), wherein the spacer has a communication portion that communicates from the outer periphery to the hollow portion.

[0014] (9) A linear actuator according to any one of (6) to (8), wherein the spacer has a convex portion on the surface facing the permanent magnet, and the periphery of the convex portion forms a holding portion.

[0015] (10) A linear actuator according to any one of (6) to (9), wherein the spacer has a recess on a surface facing the permanent magnet, and the recess forms a holding portion.

[0016] (11) A linear actuator according to any one of (6) to (8), wherein the spacer has a concave and a convex portion on the surface facing the permanent magnet, and the concave portion forms a holding portion.

[0017] (12) A method for manufacturing a shaft in which a plurality of permanent magnets are arranged inside a tubular member, the method comprising: accommodating the plurality of permanent magnets in the tubular member with gaps between adjacent permanent magnets; injecting adhesive into the gaps through openings provided on the outer surface of the tubular member corresponding to the positions of the gaps; and bonding adjacent permanent magnets together with the adhesive.

[0018] (13) A method of manufacturing a shaft according to (12), in which the tubular member has a plurality of openings for one gap, and at least one opening is used as an exhaust port when injecting adhesive.

[0019] (14) A method for manufacturing a shaft according to (12) or (13), in which a pin or wire is inserted into the opening to regulate the positions of the multiple permanent magnets housed in the tubular member.

[0020] (15) A method for manufacturing a shaft according to (12) or (13), in which a spacer is disposed between adjacent permanent magnets to form an air gap.

[0021] (16) A method for manufacturing a shaft described in (12) or (13), in which multiple permanent magnets are housed in a tubular member with the same poles facing each other, and the positions of the permanent magnets at both ends are regulated to adjust the width of the gap.

[0022] (17) A method for manufacturing a linear actuator having a cylindrical coil and a shaft passed through the inside of the coil, wherein the shaft has a plurality of permanent magnets arranged with gaps inside a cylindrical member, and adhesive is injected into the gaps through openings provided on the outer surface of the cylindrical member corresponding to the positions of the gaps, and adjacent permanent magnets are bonded together with the adhesive.

[0023] a perspective view showing the schematic configuration of a cylindrical linear motor according to a first embodiment; a view showing the configuration of a magnet joint; a perspective view showing an example of a shaft assembly jig; a front view of the shaft assembly jig shown in FIG. 3; a 5-5 sectional view of FIG. 4; a perspective view showing an enlarged view of a main part of the shaft assembly jig; a view showing another example of a spacer; a view showing another example of a spacer; a perspective view showing the schematic configuration of a cylindrical linear motor according to a second embodiment; a view showing the internal structure of the shaft; a view showing the assembly procedure of the shaft according to the second embodiment; a view showing an example of providing multiple openings in one gap; a view showing another example of a method for adjusting the width of the gap; a view showing an example of an opening that satisfies the relationship t>s; a view showing an example of a shaft using a spacer

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] First Embodiment FIG. 1 is a perspective view showing a schematic configuration of a cylindrical linear motor according to a first embodiment.

[0026] 1, the cylindrical linear motor 1 is mainly composed of a mover 2 and a shaft 10, which is a stator. The cylindrical linear motor 1 is an example of a linear actuator.

[0027] The mover 2 is composed of a cylindrical mover body 3 and a cylindrical coil 4 disposed on the inner periphery of the mover body 3. In this embodiment, the mover body 3 has a cylindrical shape, but the shape of the mover body 3 is not limited to this. For example, it may have a rectangular cylindrical shape.

[0028] The shaft 10 is configured by linearly arranging a plurality of permanent magnets (hereinafter referred to as "magnets") 11. The magnets 11 have the same shape (for example, a cylindrical shape) and are linearly arranged with a gap (spacing) G between adjacent magnets.

[0029] The magnets 11 are arranged with the same poles facing each other between adjacent magnets, i.e., with north poles facing each other and south poles facing each other, thereby forming the shaft 10 that generates magnetic flux of north and south poles alternately.

[0030] In this embodiment, spacers 12 are placed between adjacent magnets, forming gaps G between the adjacent magnets. By arranging the multiple magnets 11, 11, ... in a line with gaps G between them, the overall weight can be reduced while maintaining thrust. In other words, the amount of magnets 11 used can be reduced compared to when the magnets are closely spaced, thereby reducing the weight of the entire shaft. The width of the gap G (the axial width of the shaft 10) is set depending on the coil 4, magnets 11, etc. used. As an example, it can be set to up to 50% of the axial length of the magnet 11.

[0031] The plurality of magnets 11 are integrated by adjoining adjacent magnets together. Adjacent magnets 11 are adhered together by applying adhesive to the gaps G between the magnets.

[0032] FIG. 2 is a diagram showing the configuration of the joint of the magnet.

[0033] As described above, in this embodiment, the spacer 12 is disposed between adjacent magnets, forming the gap G between the adjacent magnets. Therefore, the thickness (axial length) of the spacer 12 is set to a thickness corresponding to the required width (axial width) of the gap G.

[0034] In this embodiment, the spacer 12 has a ring shape, and adjacent magnets are bonded together by applying adhesive 13 to the inner periphery of the spacer 12. It is preferable that the adhesive 13 be applied to the inner periphery of the spacer 12 without leaving any gaps. In other words, it is preferable that the adhesive 13 be filled into the inner periphery of the spacer 12 and bonded.

[0035] In this embodiment, the ring-shaped spacer 12 is an example of a spacer having a hollow shape with both ends open. The inner peripheral portion (hollow portion) of the spacer 12 is an example of a portion for holding the adhesive 13.

[0036] The outer diameter of the spacer 12 is preferably the same as or smaller than the outer diameter of the magnet 11. When using a spacer 12 with a smaller diameter than the outer diameter of the magnet 11, adhesive can also be applied to the outer periphery of the spacer 12.

[0037] The material of the spacer 12 is not particularly limited. It may be a magnetic material or a non-magnetic material. However, in consideration of ease of assembly, it is preferable to use a magnetic material.

[0038] The type of adhesive is not particularly limited, but a strong and fast-curing adhesive is preferable. Considering ease of assembly, it is preferable to use an adhesive with low viscosity and high fluidity. For example, an adhesive containing cyanoacrylate as the main component (so-called instant adhesive) can be used.

[0039] The shaft 10 configured as described above has a round bar (cylindrical) shape as a whole. The shaft 10 is inserted into the inner periphery of the mover 2 and is arranged concentrically with the mover 2. A predetermined gap is formed between the shaft 10 and the mover 2, and the shaft 10 is arranged concentrically with the mover 2 without contacting it.

[0040] When the coil 4 is energized, the mover 2 through which the shaft 10 is inserted generates a thrust along the shaft 10 .

[0041] [Shaft assembly jig] Fig. 3 is a perspective view showing an example of a shaft assembly jig. Fig. 4 is a front view of the shaft assembly jig shown in Fig. 3. Fig. 5 is a cross-sectional view taken along line 5-5 in Fig. 4. Fig. 6 is an enlarged perspective view of a main part of the shaft assembly jig.

[0042] The shaft assembly jig 100 is a jig used to assemble the shaft 10 configured as described above. As described above, the shaft 10 of this embodiment is made by arranging multiple magnets 11, 11, ... in a line with like poles facing each other and adjoining the magnets with an adhesive. The shaft assembly jig 100 positions the magnets 11, 11, ... so that they are coaxial.

[0043] 3 and 4 , the shaft assembly jig 100 has three positioning rods 112 on a flat bottom plate 111. The three positioning rods 112 have a round bar (cylindrical) shape and are arranged parallel to one another. The three positioning rods 112 are also arranged perpendicular to the bottom plate 111.

[0044] As shown in Figure 5, the three positioning rods 112 are arranged at a predetermined interval on the same circumference. As an example, in this embodiment, they are arranged at equal intervals (120° intervals) on the same circumference. The cylindrical space defined by a circle inscribed in these three positioning rods 112 (the space in which the circle inscribed in the three positioning rods 112 extends in the axial direction) serves as the holding space 113 for the magnet 11. In the holding space 113, the three positioning rods 112 abut against the outer periphery of the magnet 11 (they abut in line contact). This restricts movement in a direction intersecting the axis. This also means that when the magnets 11 are stacked, they are arranged coaxially with each other.

[0045] 3 and 4, the shaft assembly jig 100 has a disk-shaped top plate 114 on top of three positioning rods 112. The top plate 114 is fixedly attached to the three positioning rods 112. The top plate 114 is provided with a through hole 114A through which the magnet 11 can be inserted. The through hole 114A is arranged coaxially with the holding space 113. The magnet 11 is inserted into the holding space 113 through this through hole 114A.

[0046] Furthermore, the shaft assembly jig 100 has a weighted rod 115 as a means for axially pressing the magnets 11, 11, ... housed in the holding space 113. As shown in Figures 3 and 4, the weighted rod 115 is composed of a rod portion 115A and a weight portion 115B. The rod portion 115A has a round bar (cylindrical) shape that can be inserted into the through-hole 114A of the top plate 114. The weight portion 115B has, for example, a cylindrical shape and is provided coaxially at the top of the rod portion 115A. The weight portion 115B has a weight that is sufficient to press each magnet 11 against the spacer 12 under its own weight against the repulsive force between the magnets.

[0047] [Shaft Assembly Procedure (Shaft Manufacturing Method)] The shaft 10 is assembled as follows.

[0048] (1) Insert one magnet 11 into the holding space 113. As described above, the magnet 11 is inserted into the holding space 113 through the through-hole 114A of the top plate 114. The three positioning rods 112 abut against the outer periphery of the magnet 11 inserted into the holding space 113, restricting movement in a direction intersecting the axis.

[0049] (2) The spacer 12 is inserted into the holding space 113 and placed on the magnet 11. Figure 6 shows an example in which a spacer 12 with a smaller diameter than the magnet 11 is used. In this case, the position of the spacer 12 is adjusted as necessary so that it is positioned approximately coaxially with the magnet 11. If the spacer 12 is made of a magnetic material, the spacer 12 can be attracted and held by the magnet 11.

[0050] (3) Applying the adhesive 13. In this example, the spacer 12 has a ring shape, and the adhesive 13 is applied by filling the inner periphery of the spacer 12.

[0051] (4) Insert one magnet 11 into the holding space 113. The magnet 11 is inserted with the same pole as the magnet 11 inserted immediately before, facing each other. For example, if the previously inserted magnet 11 was inserted with its south pole facing upward, insert the next magnet 11 with its south pole facing downward. The magnet 11 is inserted into the holding space 113 while its movement in a direction intersecting the axis is restricted by the three positioning rods 112. This positions it coaxially with the magnets 11, 11, ... previously inserted into the holding space 113.

[0052] (5) The above steps (1) to (4) are repeated to form a shaft 10 of the required length.

[0053] (6) The weighted rod 115 is inserted into the through-hole 114A of the top plate 114, and a load is applied to the magnets 11, 11, ... inserted in the holding space 113. If necessary, a curing accelerator is applied to accelerate the curing of the adhesive 13. For example, when a cyanoacrylate instant adhesive is used as the adhesive, a curing accelerator (main component of which is toluidine) is used to accelerate the curing. The curing accelerator is applied, for example, through the gap in the positioning rod 112. Using the curing accelerator allows for strong adhesion in a short period of time.

[0054] (7) After the adhesive 13 has hardened, the weighted rod 115 is removed and the shaft 10 is retrieved from the holding space 113 .

[0055] The shaft 10 that generates alternating magnetic flux of north and south poles is manufactured through the above series of steps. If necessary, the shaft 10 may be reinforced by wrapping tape (for example, glass tape) around its outer periphery.

[0056] The cylindrical linear motor 1 is manufactured by passing the produced shaft 10 inside (the inner periphery of) the mover 2. The shaft 10 may be configured to be passed through the inside of the mover 2 as is, or may be housed in a cylindrical case and passed through the inside of the mover 2.

[0057] According to the cylindrical linear motor 1 of this embodiment, the use of the shaft 10 having gaps G between the magnets makes it possible to reduce the overall weight. In addition, the cylindrical linear motor 1 of this embodiment does not require a member (for example, a cylindrical case) to house the magnets 11, 11, ... of the shaft 10, making it possible to further reduce the weight and number of parts.

[0058] Furthermore, in the cylindrical linear motor 1 of this embodiment, the magnets 11, 11, ... that make up the shaft 10 are fixed in fixed positions on the shaft 10 by adhesive, so the magnets 11, 11, ... do not move when driven (when thrust is generated), and therefore, high-precision driving is possible.

[0059] [Modifications] [Spacer] The shape of the spacer 12 is not particularly limited. It may have any shape as long as it can form a specified gap (spacing) between adjacent magnets and can hold the adhesive 13 applied between the magnets to bond the adjacent magnets together. However, in order to achieve a stronger bond, a shape that ensures a large contact area of ​​the adhesive 13 with the magnet 11 is preferred. In other words, a shape that ensures a large contact area of ​​the adhesive 13 with respect to the end face, which is the bonding surface of the magnet 11, is preferred.

[0060] 7A and 7B are diagrams showing another example of a spacer, in which (A) shows a front view of the spacer and (B) shows a side cross-sectional view of the spacer.

[0061] 7 shows an example of a spacer 12 having a recess 12B on the surface 12A facing the magnet. The recess 12B serves as a holding portion for an adhesive. That is, in this example, the spacer 12 applies an adhesive to the recess 12B to bond adjacent magnets together.

[0062] 7 shows an example in which the recess 12B has a conical shape. However, the shape of the recess 12B is not limited to this. Various other shapes, such as a cylindrical shape, a pyramidal shape, or a prismatic shape, can also be used.

[0063] 8A and 8B are diagrams showing another example of a spacer, in which (A) shows a front view of the spacer and (B) shows a side view of the spacer.

[0064] Figure 8 shows an example of a spacer 12 having a protrusion 12C on the surface 12A facing the magnet. In particular, Figure 8 shows an example of a spacer having a plurality of protrusions 12C. In the spacer 12 of this example, adhesive is applied around the protrusions 12C to bond adjacent magnets together. Therefore, in the spacer 12 of this example, the periphery of the protrusions 12C forms an adhesive holding portion.

[0065] 8 shows an example in which the protrusion 12C has a truncated cone shape. However, the shape of the protrusion 12C is not limited to this. Various other shapes, such as a cylindrical shape, a cylindrical shape, a prismatic shape, or a truncated pyramidal shape, can also be used.

[0066] The spacer 12 in this example is also an example of a spacer having irregularities on the surface facing the magnet. In this case, the periphery of the protrusion 12C (the valley portion between the protrusions 12C) forms a recess, and the recess forms a holding portion for the adhesive.

[0067] [Shaft Assembly Jig] The shaft assembly jig 100 of the above embodiment is configured to position the magnets 11, 11, ... using three positioning rods 112 that circumscribe the magnets 11, 11, .... When positioning the magnets 11, 11, ... using rods (positioning rods) that circumscribe the magnets 11, 11, ..., at least two rods are sufficient. In other words, two parallel rods can restrict movement in a direction intersecting the axis, allowing the magnets 11, 11, ... to be positioned coaxially. When positioning the magnets 11, 11, ... using two rods, it is preferable that the rods be made of a magnetic material. This allows the magnets 11, 11, ... to be closely attached to the two rods using magnetic force, allowing the magnets 11, 11, ... to be stably held.

[0068] Second Embodiment FIG. 9 is a perspective view showing a schematic configuration of a cylindrical linear motor according to a second embodiment.

[0069] The cylindrical linear motor 1 of this embodiment differs from the cylindrical linear motor 1 of the first embodiment in the configuration of the shaft 10. Therefore, only the configuration of the shaft 10 will be described here.

[0070] 9, the shaft 10 of this embodiment has a cylindrical shaft case 14, and a plurality of magnets (permanent magnets) 11, 11, ... are housed and linearly arranged within the shaft case 14. Within the shaft case 14, the plurality of magnets 11, 11, ... are arranged with gaps (intervals) G provided between adjacent magnets, and with like poles facing each other. In this embodiment, the shaft case 14 is an example of a cylindrical member.

[0071] FIG. 10 is a diagram showing the internal structure of the shaft.

[0072] As shown in FIG. 10, the shaft 10 of this embodiment has a configuration in which there are no spacers between the magnets, and adjacent magnets are directly bonded to each other by adhesive 13 applied to the gap G.

[0073] The shaft case 14 is made of a non-magnetic material and has a cylindrical shape. The inner diameter of the shaft case 14 corresponds to the outer diameter of the magnets 11. Therefore, when inserted into the shaft case 14, the magnets 11, 11, ... are arranged coaxially.

[0074] The shaft case 14 has a plurality of openings 14A, 14A, ... on its outer peripheral surface. The openings 14A, 14A, ... function as injection sections (injection ports) for the adhesive 13. Therefore, the openings 14A, 14A, ... are arranged to correspond to the positions of the gaps G, G, ... between the magnets. In this embodiment, the openings 14A, 14A, ... are arranged at regular intervals along the axial direction. This interval is the same as the interval at which the gaps G are arranged.

[0075] In this embodiment, opening 14A is configured as an elongated hole extending along the axial direction of shaft 10. By configuring opening 14A as an elongated hole, air escape can be ensured when injecting adhesive 13, making it easier to inject adhesive 13. Furthermore, by configuring opening 14A as an elongated hole extending along the axial direction rather than the circumferential direction, it is possible to create a configuration that is less prone to buckling.

[0076] [Shaft Assembly Procedure (Shaft Manufacturing Method)] Fig. 11 is a diagram showing the shaft assembly procedure of this embodiment. In Fig. 11, (A) to (D) show the shaft assembly procedure in chronological order.

[0077] First, as shown in FIG. 11A, the magnets 11 are inserted into the shaft case 14. The magnets 11 are inserted by closing one end of the shaft case 14. FIG. 11A shows an example of closing one end of the shaft case 14 using a predetermined cap member 15. This cap member 15 is composed of a cylindrical fitting portion 15A and a disk-shaped flange portion 15B, and the fitting portion 15A is fitted into the inner periphery of the shaft case 14 to close one end of the shaft case 14. The fitting portion 15A has an outer diameter corresponding to the inner diameter of the shaft case 14.

[0078] The magnets 11, 11, ... are inserted so that the same poles face each other between adjacent magnets. Therefore, the magnets are inserted with the magnetic poles facing in the opposite direction one by one.

[0079] After all the magnets 11, 11, ... are inserted into the shaft case 14, as shown in FIG. 11(B), cap members 15 are attached to the end of the open side (the side where the magnets 11 are inserted) of the shaft case 14. Then, the magnets 11, 11, ... inside the shaft case 14 are sandwiched between the cap members 15 from both sides, and the overall length L of the magnets 11, 11, ... is adjusted. Here, since the magnets 11, 11, ... inside the shaft case 14 are arranged with the same poles facing each other, adjusting the overall length L adjusts the spacing between adjacent magnets. In other words, the width of the gap G formed between each magnet is adjusted. Furthermore, since each magnet 11, 11, ... has the same configuration, gaps G are formed between each magnet with the same width. Therefore, each magnet 11, 11, ... is arranged at regular intervals inside the shaft case 14. Furthermore, gaps G, G, ... are also formed at regular intervals.

[0080] The overall length L of the magnets 11, 11, ... is adjusted so that a gap G of a specified width is formed between each magnet. After adjusting the overall length L, the cap members 15 at both ends are fixed in position. This holds each of the magnets 11, 11, ... within the shaft case 14 with axial movement restricted. The cap members 15 are held in position, for example, by a holding member (not shown).

[0081] After the cap member 15 is fixed, the position between the shaft case 14 and the magnets 11, 11, ... is adjusted. That is, the position of the shaft case 14 is finely adjusted so that the opening 14A is located at the position of the gap G. By positioning the opening 14A at the position of the gap G, the gap G communicates with the outside of the shaft case 14. This makes it possible to inject the adhesive 13 into the gap G through the opening 14A.

[0082] The injection of the adhesive 13 is performed using, for example, a syringe 20. As shown in FIG. 11C , the needle of the syringe 20 is inserted into the gap G through the opening 14A, and the adhesive 13 is injected into the gap G. It is preferable that the adhesive 13 be applied without leaving any gaps. In other words, it is preferable that the gap G is filled with the adhesive 13.

[0083] In this example, the adhesive 13 is injected into the gap G using the syringe 20, but the means for applying the adhesive 13 to the gap G is not limited to this.

[0084] 11(D), after the adhesive 13 is injected into all of the gaps G, the adhesive 13 is allowed to harden, and then the cap member 15 is removed. If necessary, a hardening accelerator is applied to accelerate the hardening of the adhesive 13.

[0085] Through the above series of steps, a shaft 10 is manufactured that generates alternating magnetic flux of north and south poles. The multiple magnets 11, 11, ... that make up the shaft 10 are arranged with like poles facing each other, with a predetermined gap G between adjacent magnets. A shaft case 14 that houses the magnets 11, 11, ... is fixed to the magnets 11, 11, ... by adhesive 13 applied to the gap G. The shaft 10 has a stronger structure due to the shaft case 14. Impact resistance can also be improved. Furthermore, by fixing each magnet 11, 11, ... within the shaft case 14, the magnets 11, 11, ... do not move during operation. Therefore, when used as the shaft of a cylindrical linear motor 1, high-precision driving can be achieved.

[0086] The produced shaft 10 is passed through the inside (inner periphery) of the mover 2, thereby manufacturing the cylindrical linear motor 1.

[0087] [Modifications] [Opening of shaft case] In the above embodiment, one opening 14A is provided for one gap G, but a configuration in which multiple openings 14A are provided for one gap G may also be used.

[0088] Fig. 12 is a diagram showing an example of a case where a plurality of openings are provided in one gap. Fig. 12 shows a cross-sectional view (cross-sectional view perpendicular to the axial direction) of the shaft 10 at the arrangement portion of the gap G. Fig. 12 also shows an example of a case where two openings 14A1 and 14A2 are provided in one gap G.

[0089] When multiple openings 14A1, 14A2 are provided for one gap G, one of the openings 14A1, 14A2 can be used as an injection port for the adhesive 13, and the other can be used as an exhaust port (exhaust port). Figure 12 shows an example in which the opening 14A1 on the right side of the figure is used as the injection port for the adhesive 13. In this case, the opening 14A2 on the left side of the figure functions as an exhaust port, that is, as an air escape port.

[0090] By providing an exhaust section separate from the injection section of the adhesive 13, it is possible to easily inject the adhesive 13. In other words, the adhesive 13 can be smoothly filled into the gap G.

[0091] Furthermore, in the above embodiment, the shaft case 14 is configured to have an opening 14A for each gap G in the axial direction, but the openings 14A may be arranged across multiple gaps G. That is, openings 14A may be formed to communicate with multiple gaps G. For example, a slit-shaped opening 14A extending along the axial direction of the shaft case 14 may be formed to communicate with multiple gaps G. In this case, one opening 14A may be configured to communicate with all gaps G.

[0092] [Application to Adhesive] As described above, it is preferable that adhesive 13 be applied so as to fill gap G. Furthermore, when adhesive 13 is applied from opening 14A of shaft case 14, as in shaft 10 of the present embodiment, adhesive 13 may also be applied to opening 14A to fill the opening with adhesive 13 (so-called filling adhesion).

[0093] [Method for adjusting the gap width] In the above embodiment, the overall length L of the magnets 11, 11, ... arranged in series is adjusted to adjust the width (axial width) of the gap G formed between each magnet, but the method for adjusting the width of the gap G is not limited to this.

[0094] FIG. 13 is a diagram showing another example of a method for adjusting the width of the gap.

[0095] Figure 13 shows an example of adjusting the width of the gap G by utilizing the opening 14A of the shaft case 14. As shown in Figure 13, a positioning pin (for example, a round bar-shaped pin) 16 is inserted into the shaft case 14 through the opening 14A, and the pin 16 restricts the axial movement of the magnets 11 inside the shaft case 14, thereby defining the position of each of the magnets 11, 11, ... This makes it possible to precisely define the width of the gap G formed between each magnet (the distance between adjacent magnets).

[0096] The adhesive 13 may be injected through the same opening 14A as the pin 16, or through a separate opening 14A. That is, a plurality of openings 14A are provided for one gap G, one of which is used as a positioning opening and the other is used as an injection portion for the adhesive 13.

[0097] When adjusting the width of the gap G using the opening 14A of the shaft case 14, it is preferable that the opening 14A be formed to have a predetermined width in the circumferential direction of the shaft case 14. As an example, when the width of the gap G in the axial direction of the shaft 10 is s and the width of the opening 14A in the circumferential direction of the shaft case 14 is t, the opening 14A is formed so as to satisfy the relationship t > s.

[0098] FIG. 14 is a diagram showing an example of an opening that satisfies the relationship t>s.

[0099] As shown in Figure 14, the opening 14A is configured as an elongated hole extending along the axial direction of the shaft 10, and has a width t in the circumferential direction of the shaft case 14 that is greater than the width s of the gap G (t > s).

[0100] By configuring opening 14A as an elongated hole with a width t larger than the width s of gap G in this way, it becomes possible to use a flat positioning member 17 when positioning magnets 11, 11, ... using a positioning member. By using a flat positioning member 17 to position magnet 11, magnet 11 can be held stably and the width of gap G can be adjusted accurately. In other words, since magnet 11 can be well-seated, magnet 11 can be held stably and the width of gap G can be adjusted accurately. This also makes it possible to prevent magnet 11 from tilting.

[0101] Alternatively, a wire can be used to position the magnet 11. For example, the positioning of the magnet 11 using a wire can be achieved by forming an opening 14A at a diagonal position in a cross section perpendicular to the axis of the shaft case 14, and passing a wire through the opening 14A perpendicular to the axis. The magnet 11 is then brought into contact with the wire to position the magnet 11.

[0102] As described above, the opening 14A is preferably configured as an elongated hole extending along the axial direction of the shaft 10. This ensures air escape when injecting the adhesive 13 into the gap G, making the injection of the adhesive 13 easier. Additionally, the following effect is obtained. That is, when adjusting the width of the gap G using the opening 14A, the width can be adjusted individually for each gap G. As described above, when positioning the magnets 11 using positioning members such as pins, the shape of the opening 14A is elongated, allowing the position of the positioning members to be adjusted. This allows the width of the gap G set between each magnet (the spacing between adjacent magnets) to be adjusted. That is, since the placement position of the positioning member can be adjusted in the axial direction, the position of the magnet 11 can be adjusted in the axial direction, and as a result, the width of the gap G formed between the magnets can be adjusted. Furthermore, by being able to adjust the width of the gap G formed between each magnet, for example, when there are individual differences between the magnets 11, 11, ... used, it is possible to adjust the individual variations in magnetic flux density by adjusting the width of the gap G between each magnet (the spacing between adjacent magnets). This allows the production of a highly accurate cylindrical linear motor 1.

[0103] Furthermore, when adjusting the width of the gap G using a positioning member as in this example, the magnets 11, 11, ... may be configured to be adhered one by one. That is, a configuration can be adopted in which the magnets 11 are inserted into the shaft case 14 one by one, and then positioned and adhered one by one.

[0104] [Use of Spacers] A configuration can also be adopted in which the width of the gap between each magnet is adjusted using spacers. In this case, spacers are placed between each magnet, and the magnets 11, 11, ... are inserted into the shaft case 14.

[0105] The spacer has a shape that can hold the adhesive 13 injected from the opening 14A of the shaft case 14 between itself and the magnet 11.

[0106] Fig. 15 is a diagram showing an example of a shaft using a spacer, showing a cross section (cross section perpendicular to the axial direction) of the shaft at the position where the spacer is arranged.

[0107] 15 shows an example of a case where a ring-shaped spacer 12 is used. In this case, the spacer 12 is provided with a communication portion 12R (a so-called cutout portion) that communicates from the outer periphery to the inner periphery. As a result, the spacer 12 has a C-ring shape as a whole.

[0108] The magnet 11 is adhered by applying adhesive 13 to the inner periphery (hollow portion) of the spacer 12. To enable application of adhesive 13 to the inner periphery of the spacer 12 from outside the shaft case 14, the spacer 12 is positioned so that the position of the communication portion 12R is aligned with the position of the opening 14A of the shaft case 14. This allows the adhesive 13 to be applied (injected) to the inner periphery of the spacer 12 through the opening 14A.

[0109] In this example, the spacer 12 is an example of a spacer having a hollow shape with both ends open and having a communicating portion that communicates from the outer periphery to the hollow portion.

[0110] The spacer 12 preferably has a shape that can ensure a sufficient contact area between the magnet 11 and the adhesive 13 and can promote the flow of the adhesive 13 injected from the opening 14A of the shaft case 14. As the spacer 12, a C-ring shaped one as shown in Fig. 15, or a spacer shaped as shown in Fig. 8 can be used. In other words, a spacer having a convex or concave portion on the surface facing the magnet 11 can be used.

[0111] When using spacers, if the individual variations in magnetic flux density are to be adjusted by adjusting the width of the gap G formed between the magnets, the thickness (axial length) of the spacer used is changed to adjust the width of the gap G. The same applies to the shaft 10 of the first embodiment.

[0112] [Other embodiments] The cylindrical linear motor 1 in the above embodiment is configured to have one movable element 2 on one shaft 10, but it can also be configured to have multiple movable elements 2 on one shaft 10 (for example, multi-drive and tandem drive, etc.).

[0113] The shape of the shaft 10 is not limited to a round bar (cylindrical), but can also be a square bar (a bar shape with a polygonal cross section). The shaft 10 can also be hollow (for example, cylindrical). When the shaft 10 is hollow, a hollow magnet is used (when a spacer is used, the spacer is also hollow).

[0114] There is no particular limitation on the use of the cylindrical linear motor 1. For example, it can be mounted in a lens device and used for zoom driving, focus driving, etc. In other words, it can be used as a means for moving a lens in the optical axis direction.

[0115] [Note] In this specification, the terms "same" and "identical" mean not only completely identical but also "almost identical," which includes tolerances allowed in design and manufacturing. In this specification, the term "coaxial" means not only completely coaxial but also "almost coaxial," which includes tolerances allowed in design and manufacturing. In this specification, the term "same diameter" means not only completely identical diameter but also "almost identical diameter," which includes tolerances allowed in design and manufacturing. In this specification, the term "orthogonal" means not only completely orthogonal but also "almost orthogonal," which includes tolerances allowed in design and manufacturing. In this specification, the term "parallel" means not only completely parallel but also "almost parallel," which includes tolerances allowed in design and manufacturing. In this specification, the term "constant" means not only completely constant but also a range that is considered substantially constant (the meaning of "almost constant"). In this specification, the term "equally spaced" means not only perfectly equal intervals but also a range that is recognized as being substantially equally spaced (meaning "almost equally spaced").

[0116] DESCRIPTION OF SYMBOLS 1...Cylindrical linear motor 2...Mover 3...Mover body 4...Coil 10...Shaft 11...Magnet 12...Spacer 12A...Surface of spacer facing magnet 12B...Concave portion 12C...Convex portion 12R...Communicating portion 13...Adhesive 14...Shaft case 14A...Opening 14A1...Opening 14A2...Opening 15...Cap member 15A...Fitting portion 15B...Flange portion 16...Pin 17...Positioning member 20...Syringe 100...Shaft assembly jig 111...Bottom plate 112...Positioning rod 113...Retaining space 114...Top plate 114A...Through hole 115...Rod with weight 115A...Rod portion 115B...Plummet portion G...Gap L...Total length of magnet s...Width of gap in axial direction of shaft t...Width of opening in circumferential direction of shaft case

Claims

1. A linear actuator comprising a cylindrical coil and a shaft that passes through the inside of the coil, wherein the shaft includes a plurality of permanent magnets arranged with like poles facing each other, and wherein the plurality of permanent magnets have gaps between them, and adjacent permanent magnets are bonded together with adhesive applied to the gaps.

2. The linear actuator according to claim 1, wherein the shaft further includes a cylindrical member that houses a plurality of the permanent magnets, and the cylindrical member has an opening on its outer circumferential surface corresponding to the position of the gap.

3. The linear actuator according to claim 2, wherein the cylindrical member has a plurality of openings for each gap.

4. The linear actuator according to claim 2 or 3, wherein the opening is formed as an elongated hole extending along the axial direction of the shaft.

5. A linear actuator as described in claim 4, wherein the width of the gap in the axial direction of the shaft is s and the width of the elongated hole in the circumferential direction of the cylindrical member is t, and the gap and the elongated hole have a relationship of t > s.

6. A linear actuator according to any one of claims 1 to 3, wherein the shaft further includes a spacer disposed between adjacent permanent magnets to form the gap, the spacer having a holding portion that holds the adhesive between the spacer and the permanent magnet.

7. The linear actuator according to claim 6, wherein the spacer has a hollow shape with both ends open, and the hollow portion constitutes the holding portion.

8. The linear actuator according to claim 7, wherein the spacer has a communication portion that communicates from the outer periphery to the hollow portion.

9. The linear actuator according to claim 6, wherein the spacer has a convex portion on the surface facing the permanent magnet, and the periphery of the convex portion forms the holding portion.

10. The linear actuator according to claim 6, wherein the spacer has a recess on a surface facing the permanent magnet, the recess forming the holding portion.

11. The linear actuator according to claim 6, wherein the spacer has an uneven surface facing the permanent magnet, and the recess forms the holding portion.

12. A method for manufacturing a shaft in which a plurality of permanent magnets are arranged inside a cylindrical member, comprising: accommodating the plurality of permanent magnets in the cylindrical member with gaps between adjacent permanent magnets; injecting adhesive into the gaps through openings provided on the outer surface of the cylindrical member corresponding to the positions of the gaps; and bonding the adjacent permanent magnets together with the adhesive.

13. The method for manufacturing a shaft according to claim 12, wherein the tubular member has a plurality of openings for each gap, and at least one of the openings is used as an exhaust port when injecting the adhesive.

14. A method for manufacturing a shaft according to claim 12 or 13, wherein the positions of the plurality of permanent magnets housed in the tubular member are regulated by inserting a pin or wire into the opening.

15. The method for manufacturing a shaft according to claim 12 or 13, wherein a spacer is disposed between adjacent permanent magnets to form the gap.

16. A method for manufacturing a shaft as set forth in claim 12 or 13, wherein a plurality of the permanent magnets are housed in the cylindrical member with like poles facing each other, and the positions of the permanent magnets at both ends are regulated to adjust the width of the gap.

17. A method for manufacturing a linear actuator comprising a cylindrical coil and a shaft passed through the inside of the coil, wherein the shaft has a plurality of permanent magnets arranged with gaps between them inside a cylindrical member, and adhesive is injected into the gaps from openings provided on the outer surface of the cylindrical member corresponding to the positions of the gaps, and adjacent permanent magnets are bonded together with the adhesive.

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