JP7186956B2 - Cylindrical linear motor and method for manufacturing annular magnet - Google Patents

Description

The present invention relates to a cylindrical linear motor and a method of manufacturing an annular magnet.

Some annular magnets are magnetized in a radial orientation. In order to manufacture such an annular magnet, for example, the following manufacturing method has been proposed. First, four anisotropic magnets having a square prism shape and magnetized with the diagonal direction as the orientation direction in a plan view are prepared. Next, the four anisotropic magnets thus prepared are alternately arranged around the virtual axis, magnetically oriented in the direction toward the virtual axis and magnetically oriented in the direction away from the virtual axis, and combined. Create a magnet. Then, the obtained combined magnet body is cut and formed into an annular shape centered on the imaginary axis to manufacture an annular magnet (see, for example, Patent Document 1).

The annular magnet thus obtained is composed of four arc-shaped anisotropic magnets. Although the anisotropic magnets are magnetized in a parallel orientation, the annular magnet as a whole is pseudo-polarized. It functions as a magnet magnetized in a radial orientation.

JP 2016-225408 A

The annular magnet thus obtained can function as a pseudo radially aligned magnet as described above, but the magnetic orientation direction of each anisotropic magnet is not directed toward the center of the annular magnet.

Therefore, the magnetic field intensity on the inner peripheral side of the conventional annular magnet is inevitably smaller than that of the radially oriented annular magnet in which all the magnetic orientation directions are directed toward the center. When using a conventional annular magnet, there is a loss in terms of thrust.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for manufacturing an annular magnet capable of generating a magnetic field strength comparable to that of an annular magnet magnetized in a radial orientation. Another object is to provide a linear motor.

A tubular linear motor according to the present invention comprises a cylindrical back yoke, a single cylindrical inner tube inserted into the back yoke to form an annular gap with the back yoke, a cylindrical and windings mounted in slots provided on the outer periphery of the core, the armature inserted into the inner tube, and a cylindrical armature having an N pole and an S pole in the axial direction. a field magnet having a plurality of annular magnets arranged and stacked in the axial direction so that the poles are alternately arranged and inserted into the annular gap; and the back yoke and one end of the inner tube are capped. The back yoke and the other end of the inner tube are closed by a head cap. The magnet pieces are magnetized in a parallel orientation with different magnetic poles appearing on the inner circumference and the outer circumference, and the magnetization direction is the inner or outer magnetic pole pattern. The angle between the imaginary line connecting the centers of curvature of the inner and outer peripheries and the magnetic orientation direction at the arbitrary point is 25 degrees or less. In the tubular linear motor constructed in this way, the thrust force can be improved because the ring-shaped magnet that ensures the magnetic strength toward the inner circumference is used.

In addition, the method for manufacturing an annular magnet includes a processing step of manufacturing a magnet piece by processing a base material magnetized in parallel orientation into an arc shape, and joining a plurality of magnet pieces obtained in the processing step to form a circular magnet. and a joining step of manufacturing an annular magnet, and in the processing step, the angle formed by a virtual line connecting an arbitrary point of the magnet piece and the center of curvature of the inner and outer circumferences of the magnet piece and the magnetic orientation direction at the arbitrary point is 25 degrees or less. A magnet piece is manufactured so as to be According to the method for manufacturing an annular magnet having such a configuration, it is possible to manufacture an annular magnet that can ensure the strength of the magnetic field toward the inner periphery.

According to the tubular linear motor of the present invention, since the annular magnet capable of generating a magnetic field strength comparable to that of a radially oriented annular magnet is used, the thrust can be improved. Furthermore, according to the method for manufacturing an annular magnet, it is possible to manufacture an annular magnet capable of generating a magnetic field strength comparable to that of an annular magnet magnetized in a radial orientation.

It is a top view of an annular magnet in one embodiment. FIG. 4 is a diagram illustrating processing steps for obtaining a magnet piece from a base material; 1 is a longitudinal sectional view of a cylindrical linear motor in one embodiment; FIG. FIG. 4 is a diagram showing the relationship between the value obtained by dividing the axial length L2 of the permanent magnet of the sub-magnetic pole by the axial length L1 of the permanent magnet of the main magnetic pole and the thrust force of the cylindrical linear motor.

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, the annular magnet CM in one embodiment is formed in an annular shape by joining a plurality of arcuate magnet pieces MP. In the present embodiment, eight arc-shaped magnet pieces MP are combined in an annular shape, and both ends of each magnet piece MP in the circumferential direction are adhered with an adhesive to join and integrate them to form an annular magnet CM. there is In other words, the annular magnet CM is composed of magnet pieces MP each having a shape obtained by dividing an annular ring at equal intervals in the circumferential direction. 1 indicates the direction of magnetization. In addition, although FIG. 1 shows only the case where the magnetization direction is oriented radially inward, the magnetization direction may be oriented radially outward.

Each magnet piece MP is magnetized in a parallel orientation as shown in FIG. It is In this case, the annular magnet CM has a magnetic pole pattern in which one of the N pole and S pole appears on the inner peripheral side and the other of the N pole and S pole appears on the outer peripheral side. Although each magnet piece MP is magnetized in a parallel orientation, the magnetic orientation direction of a plurality of magnet pieces MP is joined so as to face the center of the annular magnet CM. It can function as a radially oriented magnet.

Then, when the magnet piece MP is viewed from the axial direction (the direction penetrating the paper surface of FIG. 1), an imaginary line X connecting an arbitrary point Q of the magnet piece MP and the center of curvature O to the inner and outer circumferences of the magnet piece MP and an arbitrary point The angle α between Q and the magnetic orientation direction G is set to 25 degrees or less. In this way, when the magnet piece MP is viewed in the axial direction, the angle α formed by the imaginary line X and the magnetic orientation direction G is always 25 degrees or less at any point on the magnet piece MP. The curvature of the inner and outer diameters of MP, the length in the circumferential direction, and the magnetic orientation direction G are set.

Since the annular magnet CM is constructed by joining the magnet pieces MP, the center of curvature O of the inner and outer circumferences of the magnet piece MP when viewed in the axial direction is an annular shape if dimensional errors and processing errors are ignored. It becomes the same point as the center of the magnet CM.

Here, in the case where the annular magnet CM is composed of parallel-oriented arc-shaped magnet pieces MP, the inventors found that the angle formed by the magnetic orientation direction G and the virtual line X toward both ends in the circumferential direction of the magnet pieces MP Although α becomes large and the magnetic strength on both end sides decreases, it has been found that if this angle is set to 25 degrees or less, the decrease in the magnetic strength of the annular magnet CM can be suppressed to a small extent. When the magnetic field of a cylindrical linear motor 1, which will be described later, is used, even if an annular magnet CM is used in which the angle α between the magnetic orientation direction G of the magnet piece MP and the virtual line X is set to 25 degrees or less, It was also found that by optimizing the condition of the inner diameter of the ring-shaped magnet CM, the decrease in thrust force can be suppressed to 5% or less compared to the case of using perfectly radially-oriented ring-shaped magnets.

Therefore, in the present embodiment, as described above, the annular magnet CM is composed of a plurality of arcuate magnet pieces MP magnetized in parallel orientation, and when viewed from the axial direction, any point on each magnet piece MP An imaginary line X connecting Q and the center of curvature O of the inner and outer peripheries of the magnet piece MP and the magnetic orientation direction G at an arbitrary point Q make an angle α of 25 degrees or less.

In order to manufacture such an annular magnet CM, first, as shown in FIG. 2, a rectangular parallelepiped is used as a base material B, and this base material B is magnetized in parallel orientation with the lateral direction as the magnetic orientation direction. The arrow indicated by the dashed-dotted line in FIG. 2 indicates the direction of magnetic orientation. The base material B is obtained, for example, by sintering or casting a raw material suitable for a magnet into a rectangular parallelepiped. The base material B magnetized in the parallel orientation is processed into an arc shape by cutting or the like to cut away portions other than those required as the magnet piece MP indicated by the dashed lines in FIG. 2 (machining step).

In the processing step of creating the magnet piece MP from the base material B, the center of curvature O of the inner and outer circumferences of the magnet piece MP to be obtained is arranged on a line extending from an arbitrary point of the base material B in the magnetic orientation direction. A cutting process is applied to shape the inner and outer peripheries. When the cutting work is performed in this manner, the magnetic orientation direction at the center of the finished magnet piece MP becomes the direction toward the center of the annular magnet CM, which is advantageous in terms of magnetic strength. Thus, in the present embodiment, the line connecting the center of the magnet piece MP and the center of curvature O of the magnet piece MP that coincides with the center of the annular magnet CM (chain double-dashed line in FIG. 2) and the circumference of the magnet piece MP The magnetic orientation direction at the center of the direction is matched.

When the line connecting the center of the magnet piece MP in the circumferential direction and the center of the annular magnet CM is aligned with the magnetic orientation direction of the center of the magnet piece MP, the center angle β of the magnet piece MP is set to 50 degrees. You can set the following. Then, the angle α between the magnetic orientation direction G and the imaginary line X increases toward both ends in the circumferential direction of the magnet piece MP, but the angle is 25 degrees or less at both ends.

When creating the magnet piece MP in this way, the central angle β of the magnet piece MP should be set to 50 degrees or less. .2, a minimum of eight magnet pieces MP are required. As the number of magnet pieces MP increases, the angle α formed between the magnetic orientation direction G and the imaginary line X at both ends of the magnet pieces MP becomes smaller. The smaller the angle, the smaller the distance by which the magnetic orientation direction of the magnet piece MP deviates from the center of the annular magnet CM. can.

In addition, in the case of applying cutting work to shape the inner circumference and the outer circumference so that the center of curvature O of the inner and outer circumferences of the magnet piece MP obtained on the line extending from the center of the base material B in the magnetic orientation direction is arranged, conventional techniques are used. Compared to (Patent Document 1), the volume of the unnecessary portion of the base material B that does not become the magnet piece MP can be reduced, so the processing cost and processing time can be reduced.

If the line connecting the center of the magnet piece MP in the circumferential direction and the center of the annular magnet CM coincides with the magnetic orientation direction of the center of the magnet piece MP, the magnetic strength can be increased efficiently. That is, when each magnet piece is magnetized with the direction connecting the center of each magnet piece in the circumferential direction and the center of curvature O of the inner and outer peripheries of the magnet piece as the direction of magnetic orientation, the magnetic strength can be increased efficiently. It is preferable to match the magnetic orientation direction of the center of the magnet piece MP with the line connecting the center of the magnet piece MP in the circumferential direction and the center of the annular magnet CM. The angle α between the magnetic orientation direction G and the imaginary line X should be 25 degrees or less.

The eight magnet pieces MP produced in this manner are joined in an annular shape by facing each other in the circumferential direction and adhering the end faces to manufacture the annular magnet CM (joining step). The annular magnet CM manufactured in this manner behaves as a magnet magnetized in a radial orientation, although the magnet pieces MP are oriented in parallel. In addition, since the angle α formed between the magnetic orientation direction of each magnet piece MP at an arbitrary point and the radial direction of the annular magnet CM when viewed in the axial direction is 25 degrees or less at maximum, each magnet piece MP is magnetized in parallel orientation. However, the annular magnet CM is close to radial orientation, and the field strength on the inner peripheral side can be ensured. Therefore, according to this annular magnet CM, the reduction in the field intensity is kept low compared to the perfectly radially oriented annular magnet, so the field intensity is comparable to that of the perfectly radially oriented annular magnet. can be ensured.

In this embodiment, all the magnet pieces MP have the same shape. Even if the magnet pieces MP are arcuate in this way, if the lengths in the circumferential direction are uneven, there may be cases where the annular magnet CM has a particularly low magnetic intensity portion at random, but there is no such concern. . In addition, if the circumferential lengths of the magnet pieces MP are uneven, a beautiful annular combination will be formed when joining them, and the joining process will be troublesome. Machining is also facilitated.

Next, a cylindrical linear motor 1 using an annular magnet CM will be described. As shown in FIG. 3, a cylindrical linear motor 1 in one embodiment includes an armature 2 having a cylindrical core 3 and windings 5 mounted in slots 4 provided on the outer periphery of the core 3; It comprises a field magnet 6 which has a tubular shape and in which the armature 2 is inserted so as to be axially movable and in which N poles and S poles are alternately arranged in the axial direction . 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 yoke 3a and a plurality of annular teeth 3b provided on the outer circumference of the yoke 3a at intervals in the axial direction to form a mover.

In this embodiment, as shown in FIG. 3, ten teeth 3b are arranged on the outer periphery of the yoke 3a at equal intervals in the axial direction, and the winding wire 5 is mounted between the teeth 3b, 3b. A slot 4 consisting of an air gap is formed.

In addition, each tooth 3b is annular, and except for the teeth 3b arranged at both ends of the core 3, has an isosceles trapezoidal shape in which the width of the outer peripheral end is narrower than the width of the inner peripheral end in the axial direction, The side surfaces on both sides in the axial direction are tapered surfaces that are inclined at the same angle with respect to the outer peripheral edge. The inventors' research has revealed that a favorable mass thrust density can be obtained when the internal angle θ between the side surface and the perpendicular plane in the cross section of the tooth 3b is in the range of 6 degrees to 12 degrees. Here, the mass thrust density is a numerical value obtained by dividing the maximum thrust of the cylindrical linear motor 1 having the above-described configuration by the mass. growing. Therefore, in the cylindrical linear motor 1 in which the internal angle θ between the side surface of the cross section of the tooth 3b and the perpendicular plane is in the range of 6 degrees to 12 degrees, a large mass thrust density can be obtained.
As shown in FIG. 3, the teeth 3b at the ends have a cross-sectional shape obtained by cutting the teeth 3b other than the teeth 3b at the ends in half along a plane perpendicular to the axis of the core 3. As shown in FIG. Thus, the cross-sectional shape of each tooth 3b is trapezoidal in which the width of the outer peripheral end is narrower than the width of the inner peripheral end.

Further, in this embodiment, a total of nine slots 4, which are air gaps, 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 a three-phase winding of U-phase, V-phase and W-phase. In the nine slots 4, in order from the left side in FIG. winding 5 is mounted.

The armature 2 configured in this way is attached to the outer periphery of a rod 11 that is an output shaft and is made of a non-magnetic material. Specifically, the armature 2 is held by ring-shaped sliders 12 and 13 whose left and right ends are fixed to the rod 11 in FIG.

On the other hand, in the present embodiment, the stator S consists of a cylindrical outer tube 7 made of a non-magnetic material and a back yoke 8 made of a cylindrical soft magnetic material inserted into the outer tube 7. , a cylindrical non-magnetic inner tube 9 inserted into the back yoke 8 to form an annular gap with the back yoke 8, and an annular gap between the back yoke 8 and the inner tube 9. It is composed of a magnetic field 6 having an annular magnet CM serving as a main magnetic pole and a permanent magnet 10 serving as an annular secondary magnetic pole, which are alternately stacked and inserted. The triangular marks on the ring-shaped magnet CM and the permanent magnet 10 in FIG. 3 indicate the directions of magnetization. The magnetization direction of the permanent magnet 10 of the secondary magnetic pole is the axial direction. The annular magnet CM and the permanent magnets 10 are arranged in a Halbach array, and on the inner peripheral side of the magnetic field 6, they are arranged so that the S pole and the N pole appear alternately in the axial direction. The inner diameter of the annular magnet CM and the inner diameter of the permanent magnet 10 are equal, and the outer diameter of the annular magnet CM and the outer diameter of the permanent magnet 10 are also equal.

Further, the axial length L1 of the annular magnet CM is longer than the axial length L2 of the permanent magnet 10, and in the present embodiment, 0.2≦L2/L1≦0.5 is satisfied. , the axial length L1 of the annular magnet CM and the axial length L2 of the permanent magnet 10 are set. If the axial length L1 of the annular magnet CM is increased, the magnetic resistance between the annular magnet CM and the core 3 can be reduced, and the magnetic field acting on the core 3 can be increased. can be improved.

Further, in the cylindrical linear motor 1 of the present invention, the back yoke 8 is provided on the outer peripheries of the annular magnet CM and the permanent magnet 10 . Without the back yoke 8, if the axial length L2 of the permanent magnet 10 of the secondary magnetic pole is shortened, the magnetic resistance outside the magnet at the axial central portion of the annular magnet CM increases, and the field magnetic flux decreases. When the axial length L1 of the annular magnet CM is lengthened, the degree of improvement in the thrust force of the cylindrical linear motor 1 is reduced. On the other hand, if the back yoke 8 is provided on the outer periphery of the ring-shaped magnet CM and the permanent magnet 10, a magnetic path with low magnetic resistance can be secured. Growth is suppressed. Therefore, if the axial length L1 of the annular magnet CM is made longer than the axial length L2 of the permanent magnet 10 and the tubular back yoke 8 is provided on the outer periphery of the annular magnet CM and the permanent magnet 10, the tubular linear The thrust of the 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 annular magnet MC.

The secondary magnetic pole permanent magnet 10 is a permanent magnet having a coercive force higher than that of the annular magnet CM. Residual magnetic flux density and coercive force in a permanent magnet are closely related to each other. in a relationship. In the Halbach arrangement, since a large magnetic field is applied to the permanent magnet 10 of the secondary magnetic pole in the direction of demagnetization, the coercive force of the permanent magnet 10 of the secondary magnetic pole is increased to suppress demagnetization, and a large magnetic field acts on the core 3. I am trying to make it possible. On the other hand, the strength of the magnetic field acting on the core 3 depends on the number of magnetic lines of force of the annular magnet CM. Therefore, a permanent magnet with a high residual magnetic flux density is used as the annular magnet CM to apply a large magnetic field to the core 3 . In the present embodiment, the permanent magnet 10 is made of a material having a coercive force higher than that of the annular magnet CM when the coercive force of the permanent magnet 10 is higher than that of the annular magnet CM. Therefore, the combination of the annular magnet CM and the permanent magnet 10 can be easily realized by selecting materials. In the present embodiment, the annular magnet CM is made of a material having a high residual magnetic flux density, the main components of which are neodymium, iron, and boron. It is composed of a magnet that is difficult to demagnetize by increasing the amount of heavy rare earth elements added.

A core 3 is inserted in the inner peripheral side of the stator S, and the magnetic field system 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 annular magnet CM and the permanent magnet 10 may be determined according to the movable range of the core 3 . Therefore, it is not necessary to install the annular magnet CM and the permanent magnet 10 in a range of the annular gap between the outer tube 7 and the inner tube 9 that cannot face the core 3 . The length of the back yoke 8 is equal to the length of the lamination of the annular magnet CM and the permanent magnet 10, and the annular magnet CM and the permanent magnet 10 apply a magnetic field outside the stroke range of the core 3. Consideration is given so as not to cause a decrease in thrust force.

The left ends of the outer tube 7, back yoke 8 and inner tube 9 in FIG. is blocked. Sliders 12 and 13 are in sliding contact with the inner circumference of the inner tube 9, and the sliders 12 and 13 allow the armature 2 and the rod 11 to move smoothly in the axial direction without eccentricity with respect to the magnetic field 6. . The inner tube 9 forms a gap between the outer circumference of the core 3 and the inner circumferences of the annular magnet CM and the permanent magnet 10, and cooperates with the sliders 12 and 13 to guide the axial movement of the core 3. play. Although the inner tube 9 may be made of a non-magnetic material, if it is made of a synthetic resin, the effect of improving the thrust density of the cylindrical linear motor 1 will be enhanced. If the inner tube 9 is made of non-magnetic metal, an eddy current is 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 . On the other hand, if the inner tube 9 is made of synthetic resin, no eddy current is generated, so the thrust of the cylindrical linear motor 1 can be more effectively improved and the mass of the cylindrical linear motor 1 can be reduced. When the inner tube 9 is made of synthetic resin, the friction and wear between the inner tube 9 and the sliders 12 and 13 can be reduced by making it from fluorine resin. In addition, the inner tube 9 may 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 cap 14 is provided with a connector 14a for connecting the cable C connected to the winding 5 to an external power supply (not shown), so that the winding 5 can be energized from the external power supply. The axial lengths of the outer tube 7, the back yoke 8, and the inner tube 9 are longer than the axial length of the core 3, and the core 3 is located on the left and right in FIG. You can make a stroke to

Then, for example, if the electrical angle of the windings 5 with respect to the magnetic field 6 is sensed, the energization phase is switched based on the electrical angle, and the current amount of each winding 5 is controlled by PWM control, the cylindrical linear motor 1 and the moving direction of the armature 2 can be controlled. Note that the control method described above is an example and is not limited to this. Thus, in the cylindrical linear motor 1 of this embodiment, the armature 2 acts as a mover, and the magnetic field 6 acts as a stator. Further, 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 tubular linear motor 1 includes an armature 2 having a tubular core 3 and windings 5 mounted in slots 4 provided on the outer periphery of the core 3, and a tubular armature extending inwardly. A magnetic field 6 having a plurality of annular magnets CM arranged in the axial direction so that the element 2 is movably inserted in the axial direction and the N poles and the S poles are alternately arranged in the axial direction is provided. Since the cylindrical linear motor 1 configured in this manner uses the annular magnet CM capable of ensuring the magnetic strength on the inner peripheral side, it can be compared with the case of using conventional pseudo radially oriented annular magnets. to improve thrust.

Furthermore, when the inner diameter of the annular magnet CM is set to 50 mm or more and 80 mm or less, the cylindrical linear motor 1 having the above-described configuration reduces the generated thrust even when compared to the case of using the perfectly radially oriented annular magnet. can be suppressed to 5% or less. Therefore, in the cylindrical linear motor 1 in which the armature 2 is movably inserted on the inner peripheral side as a mover and the magnetic field 6 serves as a stator, when the annular magnet CM is used, the inner diameter is set to 50 mm or more and 80 mm or less. With this setting, it is possible to obtain a thrust that is comparable to the use of perfectly radially oriented annular magnets.

The cylindrical linear motor 1 includes an armature 2 having a cylindrical core 3 and windings 5 mounted in slots 4 provided on the outer periphery of the core 3, and a cylindrical armature extending inwardly. 2 is movably inserted in the axial direction and has a magnetic field 6 in which N poles and S poles are alternately arranged in the axial direction. It has an annular magnet CM magnetized in the direction, a permanent magnet 10 magnetized in the axial direction, and a cylindrical back yoke 8 arranged on the outer periphery of the annular magnet CM and the permanent magnet 10. The axial length L1 of the annular magnet CM is longer than the axial length L2 of the permanent magnet 10 of the secondary magnetic pole.

When the cylindrical linear motor 1 is configured in this manner, the axial length L1 of the main pole annular magnet CM is increased to reduce the magnetic resistance between the main pole annular magnet CM and the core 3. In addition, even if the axial length L2 of the permanent magnet 10 of the secondary magnetic pole is shortened, since the back yoke 8 is provided, an increase in magnetic resistance can be suppressed and the magnetic field applied to the core 3 can be increased.

Therefore, according to the cylindrical linear motor 1 of the present embodiment, the magnetic resistance between the annular magnet CM of the main pole and the core 3 can be reduced while suppressing the demagnetization of the permanent magnet 10 of the sub pole. can significantly improve thrust.

If the secondary magnetic pole permanent magnet 10 has a higher coercive force than the main magnetic pole annular magnet CM, the main magnetic pole permanent magnet 10 is suppressed from being demagnetized while a large magnetic field is applied thereto. A permanent magnet with a high residual magnetic flux density can be used for the annular magnet CM.

Further, if the axial length L1 of the annular magnet CM of the main magnetic pole is made longer than the axial length L2 of the permanent magnet 10 of the secondary magnetic pole, the magnetic field 6 can act on the core 3 with a large magnetic field. There is an optimum relationship between the axial length L1 of the magnetic pole annular magnet CM and the axial length L2 of the secondary magnetic pole permanent magnet 10 . FIG. 4 shows the relationship between the axial length L2 of the secondary magnetic pole permanent magnet 10 divided by the axial length L1 of the annular magnet CM serving as the main magnetic pole and the thrust force of the tubular linear motor 1 . As a result of intensive research, the inventors have found that the axial length L1 of the annular magnet CM of the main magnetic pole and the axial length L2 of the permanent magnet 10 of the secondary magnetic pole are 0.15≦L2/ It has been found that if L1≦0.6 is set, a thrust that is 95% or more of the thrust when the value of L2/L1 is set to an ideal value can be secured.

Therefore, the axial length L1 of the annular magnet CM of the main magnetic pole and the axial length L2 of the permanent magnet 10 of the secondary magnetic pole in the cylindrical linear motor 1 are set so as to satisfy 0.15≦L2/L1≦0.6. If set, the thrust can be further improved. Furthermore, as can be understood from FIG. 4, the axial length L1 of the annular magnet CM of the main magnetic pole and the axial length L2 of the permanent magnet 10 of the secondary magnetic pole satisfy 0.2≦L2/L1≦0.5. With this setting, the thrust of the cylindrical linear motor 1 can be improved more effectively because it is possible to secure 98% or more of the thrust when the value of L2/L1 is set to the ideal value.

Further, in the cylindrical linear motor 1 of the present embodiment, the teeth 3b have a trapezoidal cross-sectional shape in which the width of the outer peripheral ends is narrower than the width of the inner peripheral ends. The cross-sectional area of the magnetic path at the inner peripheral end is larger than in the case of a rectangular shape. Therefore, in the cylindrical linear motor 1 configured in this way, it becomes easy to secure a large cross-sectional area of the magnetic path, magnetic saturation can be suppressed when the winding 5 is energized, and a larger magnetic field can be generated, resulting in a larger thrust. can be generated. In order to improve the thrust force, the cross-sectional shape of the teeth 3b may be trapezoidal, but the cross-sectional shape may be rectangular or other shapes.

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, 3... Core, 4... Slot, 5... Winding, 6... Field, B... Base material, CM Annular magnet, G: Magnetic orientation direction, MP: Magnet piece, O: Curvature center, Q: Arbitrary point, X: Virtual line

Claims (2)

a cylindrical back yoke;
a single cylindrical inner tube inserted into the back yoke to form an annular gap therebetween;
an armature having a cylindrical core and windings mounted in slots provided on the outer periphery of the core and inserted into the inner tube;
a field magnet inserted into the annular gap, having a plurality of tubular annular magnets arranged and laminated in the axial direction so that N poles and S poles are alternately arranged in the axial direction; ,
one end of the back yoke and the inner tube is closed by a cap,
The back yoke and the other end of the inner tube are closed by a head cap,
The annular magnet is formed into an annular shape by joining a plurality of arc-shaped magnet pieces,
Each magnet piece has a magnetic pole pattern in which different magnetic poles appear on the inner circumference and the outer circumference, and the magnetization direction is inside or outside, and is magnetized in parallel orientation,
An imaginary line connecting an arbitrary point on each magnet piece and the center of curvature of the inner and outer peripheries of the magnet piece and the magnetic orientation direction at the arbitrary point form an angle of 25 degrees or less.
A cylindrical linear motor characterized by: a processing step of manufacturing a magnet piece by processing a base material magnetized in parallel orientation into an arc shape;
a joining step of joining a plurality of magnet pieces obtained in the processing step to manufacture an annular magnet;
In the processing step, the magnet piece is manufactured so that the angle between the virtual line connecting the arbitrary point of the magnet piece and the center of curvature of the inner and outer peripheries of the magnet piece and the magnetic orientation direction at the arbitrary point is 25 degrees or less. A method for manufacturing an annular magnet, characterized by:

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