JP4692713B2 - Linear actuator - Google Patents

Description

  The present invention relates to a linear actuator having a simple structure and high performance.

  Solenoids are widely used in all industries as actuators for obtaining small strokes. However, a) The linearity of the thrust with respect to the current is not good for the solenoid. b) Thrust generated by energization decreases rapidly with respect to displacement. c) Since thrust can be generated only in one direction, other means such as a coil spring is required when returning to the original position. Therefore, it is not suitable for application to applications that require positioning operation.

On the other hand, linear actuators are used as compressor motors and the like because they do not have the disadvantages a) to c) described above and can be driven with less loss by resonating together with a spring. And since the compressor using this linear actuator can exhibit excellent performance, such as high efficiency, utilization for a refrigerator, a freezer, or an air conditioner is anticipated (for example, refer to patent documents 1).
JP2003-339147A.

However, the conventional permanent magnet type linear actuator does not have the disadvantages of a) to c). However, when it is desired to obtain a large stroke, either a double power source (a power source capable of flowing positive and negative currents) is used, or a linear actuator is used. It is necessary to increase the size of the actuator itself.
Further, the magnetic center (thrust center, stroke center) is at the center of the linear actuator, and in order to use the linear actuator with the maximum stroke, it was necessary to flow current positively or negatively. That is, in a linear actuator having a maximum stroke of 20 mm, a driver capable of flowing positive and negative currents is prepared, and a displacement of ± 10 mm is ensured by flowing positive and negative currents. As a result, it is necessary to obtain a stroke of 20 mm.

  The present invention has been made in view of the above circumstances, and can be driven by a single power source without complicating the configuration as compared with a conventional linear actuator, and ensures a sufficient thrust even at the center of the linear actuator. Provided is a linear actuator that can be used.

In order to achieve the above object, the present invention proposes the following means.
The invention according to claim 1 includes a stator formed in a cylindrical body and at least one iron member, and is inserted into the stator and exposed outward from both end openings of the cylindrical body. As described above, a mover provided so as to be able to reciprocate in the axial direction of the cylindrical body with respect to the stator, a magnetic pole facing the iron member and perpendicular to the reciprocating direction, and the stator A linear actuator comprising at least one permanent magnet provided along the reciprocating direction and a coil provided on the stator, wherein the permanent magnet has a magnetomotive force of the iron member. In a state where the coil is configured to be asymmetric with respect to the reciprocating direction and no current flows through the coil, the iron member is disposed at a reference position that is close to the strong side of the magnetomotive force in the reciprocating direction. The coil In the state of flowing, the magnetomotive force of the coil cancels the magnetomotive force of the strong side of the magnetomotive force of the permanent magnet, and strengthens the magnetomotive force of the weak side of the magnetomotive force of the permanent magnet. Thus, the magnetomotive force of the weak side region is larger than the magnetomotive force of the strong side region.

According to the first aspect of the present invention, the magnetomotive force of at least one permanent magnet provided in the stator along the reciprocating direction is configured asymmetrically in the reciprocating direction of the iron member. The iron member provided in the mover causes a current to flow through the coil, and the mover moves from the reference position by the magnetic force of the coil . Further, when the current flowing through the coil is turned off to be in a non-driven state, the iron member automatically returns to the reference position in the reciprocating direction by the return action by the permanent magnet .

In this case, since the mover is offset with respect to the magnetomotive force of the permanent magnet, the reciprocating motion of the iron member can be performed by a current in one direction (single power supply), and also compared with the case where it is not offset. The directional stroke can be approximately doubled.
Further, the positioning operation can be performed by adjusting the magnitude of the current.
Further, it is possible to offset the thrust with respect to the displacement so that the thrust at the reference position of the mover is zero and to obtain a thrust substantially proportional to the displacement of the mover of the linear actuator.
As a result, thrust can be obtained even when the mover is in the center of the linear actuator (that is, when the displacement is zero in the conventional linear actuator).

  The invention according to claim 2 is the linear actuator according to claim 1, wherein the permanent magnet is configured such that the thickness in the magnetic pole direction is thick at one end side of the reciprocating range of the iron member, and the other end. The magnetomotive force is asymmetrically formed by the thin side.

  According to the second aspect of the present invention, since the thickness of the permanent magnet in the magnetic pole direction is thick at one end side of the reciprocating range of the iron member and the other end side is thin, the magnetomotive force is asymmetric in the reciprocating direction. The mover is offset with respect to the magnetomotive force of the permanent magnet.

  The invention according to claim 3 is the linear actuator according to claim 1, wherein the permanent magnet has a material on one end side of the permanent magnet at an axial position in a reciprocating range of the iron member. It is characterized in that the magnetomotive force is formed asymmetrically by adopting a configuration different from the above.

  According to the invention which concerns on Claim 3, the magnetomotive force is varied by making the material of a permanent magnet differ in the one end side and other end side of a backward movement range. As a result, the magnetomotive force becomes asymmetric in the reciprocating direction, and the mover is offset with respect to the magnetomotive force of the permanent magnet.

  The invention according to claim 4 is the linear actuator according to claim 1, wherein the permanent magnet is arranged close to one end side of the axial position of the reciprocating range of the iron member and arranged on the other end side. The magnetomotive force is formed asymmetrically by adopting a configuration that does not.

  According to the invention which concerns on Claim 4, a permanent magnet is set near the one end side of the axial direction position of the reciprocation range of an iron member, and it is set as the structure which is not arrange | positioned at the other end side. Therefore, there is a magnetomotive force on one end side of the permanent magnet and no magnetomotive force on the other end side. Therefore, the magnetomotive force becomes asymmetric in the reciprocating direction, and the mover is offset with respect to the magnetomotive force of the permanent magnet. The

  The invention according to claim 5 is the linear actuator according to any one of claims 1 to 4, wherein a gap between the permanent magnet on the one end side and the iron member is set to the permanent on the other end side. A gap that is smaller than the gap between the magnet or the stator and the iron member is provided.

  According to the invention which concerns on Claim 5, it adjusts so that the urging | biasing force with respect to a needle | mover may be weakened according to a use by forming the clearance gap between the said permanent magnet or stator and iron member of the other end partly wide. can do.

The invention according to claim 6 is the linear actuator according to any one of claims 1 to 5, wherein a surface facing the iron member is configured to be flush with a reciprocating direction of the mover. It is characterized by that.
According to the invention which concerns on Claim 6, since the clearance gap between a permanent magnet or a stator and the iron member of a needle | mover is kept constant in a reciprocating direction, magnetic flux leakage is suppressed, As a result, with respect to a needle | mover It becomes possible to strengthen the urging force.

According to the linear actuator of the present invention, the mover can be driven by a single power source, and the stroke can be doubled without increasing the motor size.
Further, the amount of permanent magnet used can be halved compared to a conventional linear actuator.
In addition, it is possible to automatically return to the reference position by cutting off the current flowing through the magnet coil and setting it in a non-driven state.
Further, the positioning operation can be performed by adjusting the magnitude of the current, and the thrust at the reference position of the mover is made zero and the mover is in the center of the linear actuator (that is, the displacement of the conventional linear actuator is zero). Even in this case, a thrust is obtained, and a thrust substantially proportional to the displacement of the mover can be obtained.

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing a linear actuator according to a first embodiment of the present invention.
The linear actuator 11 of this embodiment includes a yoke (stator) 12, a mover 13 provided inside the yoke 12 so as to be reciprocable, and a first pair of permanent magnets (permanent). Magnets) 14 and 15, a second pair of permanent magnets (permanent magnets) 16 and 17 fixed to the yoke 12, and two coils 18 and 19 fixed to the yoke 12 . Further, as shown in FIG. 3, by elastically deforming itself, the movable element 13 is supported so as to be reciprocally movable with respect to the yoke 12, and the movable element is brought to a reference position in the reciprocating direction in a non-driven state. Two leaf springs 3 may be provided .

  As shown in FIG. 1, the yoke 12 has a rectangular tube shape as a whole by forming a through hole 21 at its center position. The through hole 21 has two cylindrical surface portions 22 which are formed in a shape in which the inner peripheral surface of the cylinder is cut in parallel at two places with a predetermined interval and opposed to each other in a separated state. The two cylindrical surface portions 22 have the same diameter, the same length, and the same width, and are arranged coaxially.

  The yoke 12 has a rectangular tube shape as a whole by forming a through hole 21 at its center position. The through-hole 21 has two cylindrical surface portions 22 which are formed in a shape in which the inner peripheral surface of the cylinder is cut in two places parallel to the axis thereof at a predetermined interval and which are opposed to each other in a separated state. A flat surface portion 23 extending outward from the edge portions of both ends along the direction connecting the cylindrical surface portions 22, and an orthogonal edge to the flat surface portion 23 from the opposite edge portion with respect to each cylindrical surface portion 22 of each flat surface portion 23. A flat surface portion 24 extending outward and a planar inner surface portion 25 extending in a direction connecting the cylindrical surface portions 22 and connecting corresponding ones of the flat surface portions 24 are provided. Here, the two cylindrical surface portions 22 have the same diameter, the same length, and the same width, and are arranged coaxially.

The yoke 12 is made of a laminated steel plate formed by punching a thin steel plate with a press to form a base member, and joining the base member while laminating a plurality of base members in the penetrating direction of the through hole 21. Yes.
As shown in FIG. 3, the mover 13 has a cylindrical shape with a male screw portion 13a formed at the tip, and a shaft 13b that reciprocates in the axial direction, and a shaft 13b that is inserted into the shaft 13b. And an iron member 30 as a movable magnetic pole fixed at an intermediate position in the direction.

  As shown in FIG. 2, the permanent magnets 14 and 15 are made of, for example, ferrite magnets of the same material having the same length and the same width, which are formed by cutting a cylinder in parallel at two places at predetermined intervals. The permanent magnet 14 is formed so that the radius of the arc on the inner diameter side is smaller than that of the permanent magnet 15, that is, the thickness is thicker. The permanent magnets 14 and 15 are arranged coaxially with each other, aligned in the circumferential direction and adjacent to each other in the axial direction, and are bonded and fixed to one cylindrical surface portion 22. The permanent magnet 14 and the iron member 30 are connected to each other. The gap (gap) to be formed is smaller than the gap formed by the permanent magnet 15 and the iron member 30. Here, these permanent magnets 14 and 15 are of radial anisotropy having magnetic poles in a direction orthogonal to the axial direction, and the arrangement of the magnetic poles is reversed. One permanent magnet 14 in the through direction of the through hole 21 has an N pole arranged on the outer diameter side and an S pole arranged on the inner diameter side, and the other permanent magnet 15 has an N pole arranged on the inner diameter side. Is arranged on the outer diameter side.

  As shown in FIG. 2, the permanent magnets 16 and 17 are made of, for example, ferrite magnets of the same material having the same length and the same width, which are formed by cutting a cylinder in parallel at two places at predetermined intervals. The permanent magnet 16 is formed so that the radius of the arc on the inner diameter side is smaller than that of the permanent magnet 17, that is, the thickness is thicker. The permanent magnets 16 and 17 are coaxial with each other, are aligned in the circumferential direction and are arranged adjacent to each other in the axial direction, and are bonded and fixed to one cylindrical surface portion 22. The permanent magnet 16 and the iron member 30 are fixed to each other. The gap (gap) to be formed is smaller than the gap formed by the permanent magnet 17 and the iron member 30. Here, these permanent magnets 16 and 17 are of radial anisotropy having magnetic poles in a direction perpendicular to the axial direction, and the arrangement of the magnetic poles is reversed. Further, one permanent magnet 16 in the penetration direction of the through hole 21 has the S pole arranged on the outer diameter side and the N pole arranged on the inner diameter side, and the other permanent magnet 17 has the S pole arranged on the inner diameter side. Is arranged on the outer diameter side.

  As described above, the first pair of permanent magnets 14 and 15 and the second pair of permanent magnets 16 and 17 are permanent magnets that are positioned in the penetrating direction of the through hole 21, and the magnetic poles on the inner diameter side, that is, the mover 13 side. It is reversed. That is, the permanent magnet 14 and the permanent magnet 16 that are aligned in the penetration direction of the through hole 21 have the inner poles opposite to each other, and the permanent magnet 15 and the permanent magnet 17 that are aligned in the penetration direction of the through hole 21 are also mutually. The magnetic pole on the inner diameter side is reversed.

  As shown in FIG. 3, the coil 18 has a winding drum 32 attached so as to surround a cylindrical surface portion 22 formed so as to protrude inwardly from the yoke 12, and a conductive wire is wound around the winding drum 32 in multiple layers. ing. In the coil 19, a winding drum 32 is similarly attached to a cylindrical surface portion 22 corresponding to the cylindrical surface portion 22 formed at a position facing the cylindrical surface portion 22 with the yoke 12 interposed therebetween, and a conductive wire is wound around the winding drum 32 in multiple layers. Configured.

The two leaf springs 3 are spaced apart in the axial direction of the mover 13 and are disposed with the yoke 12 interposed therebetween. The two leaf springs 3 have the same shape, are stamped from a metal plate having a uniform thickness, and are formed in a “8” shape when viewed from the axial direction of the mover 13. Through holes 3a (shown in FIG. 3) for supporting the front end or the rear end of the movable element 13 are formed at locations corresponding to portions where the central line of “8” intersects. Further, through holes 3b and 3c having a size capable of sufficiently passing the above-described coil 18 or 19 inside are formed at locations corresponding to the inside of the circle of “8”.
Further, small holes 3 d and 3 e for fixing the leaf spring 3 to the yoke 12 are formed at locations corresponding to the uppermost part and the lowermost part of “8”.

  Each leaf spring 3 supports the mover 13 at an intermediate position in the axial direction of the coil 18. More specifically, as shown in FIG. 3, one leaf spring 3 that supports the tip of the mover 13 is fixed to the through hole 3a through the tip of the mover 13, and is passed through the small hole 3d. These are fixed to the yoke 12 at a position farther from the center of the movable element 13 than the coil 18 or 19 by a screw (not shown) and a screw (not shown) passed through the small hole 3e. The other leaf spring 3 that supports the rear end of the mover 13 is fixed to the through hole 3a through the rear end side of the mover 13, and the mover's screw is passed through the small holes 3d and 3e. It is fixed to the yoke 12 at a position farther than the coil 18 or 19 from the center.

  One leaf spring 3 causes the coil 18 to protrude from the through hole 3b to the distal end side of the mover 13, and also causes the coil 19 to protrude from the through hole 3c to the distal end side of the mover 13. The coil 18 is projected from the hole 3b to the rear end side of the mover 13, and the coil 19 is also projected from the through hole 3c to the rear end side of the mover 13. The distance between the two leaf springs 3 along the axial direction of the mover 13 is narrower than the dimension of the coil 18 or 19 along the same direction, and the through holes 3b and 3c avoid interference with the coil 19. It plays the role of “escape”.

  The linear actuator 11 having the above structure, when no current is passed through both the coils 18 and 19, passes the yoke 12 through the yoke 12, the permanent magnet 16, and the iron member 30 in this order as shown by a curve a in FIG. 4. A magnetic flux is formed by the connecting loop, and a magnetic flux is formed by the loop connecting through the yoke 12, the iron member 30, and the permanent magnet 14 as shown by the curve b.

The yoke 12, permanent magnet 16, iron member 30, mover 13, iron member 30, permanent member 14 , yoke 12 , permanent magnet 15, iron member 30, mover 13, iron are formed by the loop composed of the curves a and b. A large loop magnetic flux φ connecting the member 30, the permanent magnet 17 and the yoke 12 in this order is formed.

The large-loop magnetic flux φ is asymmetric with respect to the reciprocating direction of the linear actuator 11, and a thrust P is generated in the mover 13 in the arrow direction of FIG. 4 . For this reason, the mover 13 is stopped at the reference position in a state where it is offset from the center of the linear actuator 11.

Next, the operation of the linear actuator 11 of this embodiment will be described.
In the non-driven state, the movable element 13 generates a magnetomotive force of the permanent magnet from the permanent magnet 16 to the permanent magnet 14, and a thrust P is generated in the direction of the arrow in FIG. The thrust P is causes stop to the reference position the mover 13 in a state of being offset from the center of the linear actuator 11.

First, by applying a direct current to both the coils 18 and 19, the magnetic flux is guided from the S pole to the N pole, whereby the outer peripheral portion of the yoke 12, the cylindrical surface portion 22, the permanent magnet 14 , the iron member 30, and the mover 13. Two symmetrical loops that circulate in the order of the outer periphery of the iron member 30, the permanent magnet 16 , and the yoke 12 are formed.
At the same time, between the first permanent magnet 15 and the second permanent magnet 17, the magnetic flux is generated from the outer peripheral portion of the yoke 12, the cylindrical surface portion 22, the permanent magnet 15 , the iron member 30, the mover 13, the iron member 30, and the permanent magnet. Two symmetrical loops that circulate in the order of the magnet 17 and the outer periphery of the yoke 12 are formed.

Therefore, magnetic flux is generated between the permanent magnet 16 and the permanent magnet 14 in the direction from the permanent magnet 16 to the permanent magnet 14, and between the permanent magnet 17 and the permanent magnet 15 in the direction from the permanent magnet 15 to the permanent magnet 17. However, the magnetic flux in the iron member 30 becomes dense between the permanent magnet 17 and the permanent magnet 15 , and conversely, between the permanent magnet 16 and the permanent magnet 14 , the magnetomotive force due to the permanent magnets 14, 16 is canceled, and the magnetomotive force Becomes smaller.
As a result, the movable element 13 acts thrust towards the positive direction (the right side in FIG. 4), the movable element 13 moves in the same direction by being pressed by the force.

The relationship between the position F of the linear actuator 11 according to the present invention in which the iron member 30 of the mover 13 is offset in the reciprocating direction and the linear actuator 11 in which the conventional mover 13 is not offset and the magnitude F of the thrust is as follows. The relationship is as shown in FIG.
That is, in the conventional linear actuator 11 in which the mover 13 is not offset, when the mover 13 is positioned at the intermediate position Q in the axial direction in the yoke 12 and is driven and reciprocated therefrom, a loop indicated by a broken line X is formed. Draw. On the other hand, the linear actuator 11 according to the present invention in which the mover 13 is offset is displaced from the intermediate position in the axial direction in the yoke 12 and is driven from the reference position R to reciprocate. A loop indicated by Y will be drawn.

According to the linear actuator of the first embodiment, it is possible to drive the reciprocating entire range of the movable member at single power supply. As a result, the stroke that can be driven with a current in one direction can be approximately doubled.
The positioning operation can be performed by adjusting the magnitude of the current, and the movable element automatically returns to the reference position by cutting the current.

Further, it is possible to offset the thrust with respect to the displacement so that the thrust at the reference position of the mover is zero and to obtain a thrust substantially proportional to the displacement of the mover of the linear actuator.
As a result, thrust can be obtained even when the mover is in the center of the linear actuator (that is, when the displacement is zero in the conventional linear actuator).
In this embodiment, since the gap formed by the permanent magnet 14 and the permanent magnet 16 is wider than the gap formed by the permanent magnet 15 and the permanent magnet 17 and the iron member 30, the biasing force against the mover 13 is formed. Can be adjusted to weaken as needed.

Moreover, since the permanent magnet 15 and the permanent magnet 17 are formed thinner than the permanent magnet 14 and the permanent magnet 16, the manufacturing cost can be reduced by making the permanent magnet thinner. Further, with respect to thrust and the like, it is possible to ensure the same performance as that not lost.
Further, by forming the permanent magnets 15 and 17 thin, the amount of permanent magnets used can be reduced, and the manufacturing cost can be reduced.

FIG. 6 shows an actuator according to a second embodiment of the present invention.
In this embodiment, the difference from the first embodiment is that the area of the cylindrical surface portion 22 of the yoke 12 in which the permanent magnets 14 and 16 are arranged is changed according to the thickness of the permanent magnets 14 and 16. The surface of the first pair of permanent magnets 14, 15 and the second pair of permanent magnets 16, 17 facing the iron member 30 is configured to be flush with the moving direction of the mover 30. .

According to the actuator 11 of the second embodiment, the permanent magnet 16 positioned at one end of the actuators 11 become dense magnetic flux to the permanent magnet 14, a thrust F of the one end side direction is generated as a result . Further, in addition to the effects of the first embodiment, a gap formed by the first pair of permanent magnets 14 and 15 disposed on the yoke 12 and the iron member 30 of the second pair of permanent magnets 16 and 17 is formed. Since the magnetic flux leakage is suppressed while being kept constant in the reciprocating direction, the urging force against the mover 13 can be increased.

FIG. 7 shows an actuator according to a third embodiment of the present invention.
In this embodiment, the difference from the first embodiment is that the permanent magnets 14, 15, 16, and 17 are formed to have the same diameter, the same length, and the same width, and the material of the permanent magnets 14, 16 and the permanent magnets 15, 17 The permanent magnets 14 and 16 are made of a ferromagnetic material as compared with the permanent magnets 15 and 17.
Specifically, the permanent magnets 14 and 16 may be made of samarium cobalt, and the permanent magnets 15 and 17 may be made of ferrite magnets.

According to the actuator 11 of the third embodiment, a permanent magnet 16 positioned at one end of the actuators 11 become dense magnetic flux to the permanent magnet 14, a thrust F of the one end side direction is generated as a result . Also, in addition to the effect of the first embodiment, the gap formed by the first pair of permanent magnets 14 and 15 arranged on the yoke 12 and the iron members 30 of the second pair of permanent magnets 16 and 17 Is kept constant in the reciprocating direction, and magnetic flux leakage is suppressed, so that it is possible to increase the urging force on the mover 13.

FIG. 8 shows an actuator according to a fourth embodiment of the present invention.
In this embodiment, the difference from the first embodiment is that the permanent magnets 14A and 16A are brought closer to one end side of the axial position of the reciprocating range of the iron member 30 and protruded toward the iron member 30 toward the inner surface of the cylindrical surface portion 22. The magnetomotive force is asymmetrically formed by disposing them and not arranging them on the other end side.

According to the actuator 11 of the fourth embodiment, it becomes dense magnetic flux from the permanent magnet 16A located on one side of the actuators 11 to the permanent magnet 14A, the thrust F of the one end side direction is generated as a result . Further, in addition to the effects of the first embodiment, the permanent magnets 14A and 16A are brought closer to one end with respect to the yoke 12, so that thrust can be generated in the mover even when the mover has no axial displacement.

Further, since the gap in the region formed by the yoke 12 and the iron member 30 where the permanent magnets 14A and 16A are not arranged is formed wider than the gap formed by the permanent magnet 14A and the permanent magnet 16A, the mover 13 The biasing force against can be adjusted to weaken as necessary.
In addition, since the number and size of permanent magnets are reduced and the cylindrical surface 2 of the yoke 12 is kept flush, there is no need to embed the permanent magnets 14A and 16A in the yoke 12. Cost can be reduced.
Further, the manufacturing cost can be reduced by reducing the amount of the permanent magnet used to ½.

FIG. 9 shows an actuator according to a fifth embodiment of the present invention.
In this embodiment, the fourth embodiment is different from the fourth embodiment in that the area where the permanent magnets 14A and 16A of the cylindrical surface portion 22 of the yoke 12 are arranged is formed to have a larger diameter by the thickness of the permanent magnets 14A and 16A. The magnets 14A and 16A are embedded in the yoke 12, and the cylindrical surface 22 facing the iron member 30 is configured to be flush with the reciprocating direction of the mover 30 in both the areas where the permanent magnets 14A and 16A are present and not. is there.

  According to the actuator 11 of the fifth embodiment, the gap formed by the iron member 30 is constant in the reciprocating direction in both the region where the permanent magnets 14A and 16A arranged in the yoke 12 are present and the region where the permanent magnets 14A are not present. Since it is maintained and magnetic flux leakage is suppressed, the urging force against the movable element 13 can be increased.

FIG. 10 shows an actuator according to a sixth embodiment of the present invention.
In this embodiment, the fourth embodiment is different from the fourth embodiment in that two iron members 30 of the mover 13 are arranged in the reciprocating direction of the mover 13, and a first pair of iron members 30 corresponding to the respective iron members 30. The permanent magnets 14, 15 and the second pair of permanent magnets 16, 17 are brought close to one end side in the reciprocating direction of the yoke 12, and are disposed so as to protrude from the cylindrical surface portion 22 in the direction of the iron member 30.

According to the actuator 11 of the sixth embodiment, the magnetic flux from the permanent magnets 16 which are arranged close to one end of the actuators 11 to the permanent magnet 14, dense magnetic flux to the permanent magnet 15 from the permanent magnet 17 As a result, a thrust in one end side direction is generated. In this case, since the two iron members 30 are provided on the mover 13, the stroke is halved, but a double thrust 2F can be obtained.

In the linear actuator 11, when a current is passed through the coil so as to move the mover 13 in the positive direction, a magnetic flux is generated by the magnetomotive force generated thereby, so that the mover can be moved reliably.
In addition, when the first pair of permanent magnets 14 and 15 and the second pair of permanent magnets 16 and 17 are brought closer to the other axial end of the iron core of the yoke, the current is left when no current flows through the coil. It becomes the position of the offset state that shifts in the direction.

  In the linear actuator, each leaf spring 3 is supported by the stator 2 at a position farther from the coils 18 and 19 with the mover as a base point while avoiding interference with the coils 18 and 19. Thereby, the bulky coils 18 and 19 and the two leaf springs 3 can be arranged closer to each other. Therefore, the size of the linear actuator can be reduced.

  In the above embodiment, the winding cylinder 32 surrounds the cylindrical surface portion 22 formed so as to protrude inward from the yoke 12 and the protruding shape portion of the cylindrical surface portion 22 corresponding to the cylindrical surface portion 22, and these windings Although the structure in which the conducting wires are wound around the cylinder 32 in a multiple manner has been described, the conducting wires may be wound at both side positions of the intermediate portion connecting the cylindrical surface portion 22 corresponding to the cylindrical surface portion 22 of the iron member constituting the magnetic circuit in the yoke 12. Magnetism may be generated.

Further, in the above embodiment, as the permanent magnet, a rare earth system such as neodymium or samarium cobalt can be used in addition to the ferrite magnet described above.
Further, in the above-described embodiment, a description is given of a case of a two-pole linear actuator composed of a first pair of permanent magnets 14 and 15, a second pair of permanent magnets 16 and 17, and coils 18 and 19. Although described, three or more poles may be provided.
In addition to the leaf spring, the bearing may be a rolling bearing such as a sliding bearing or a ball bush.
Further, components such as the size, thickness, material, and arrangement of the magnet can be selected without departing from the spirit of the present invention without being limited to the above embodiment.

It is a front view which shows the linear actuator which concerns on 1st Embodiment of this invention. It is the longitudinal cross-sectional view seen from the right side surface of FIG. It is a partially broken perspective view showing a linear actuator. It is explanatory drawing which shows the state of the magnetic flux when the electric current is not flowing into the coil. It is a figure which shows the relationship between the displacement of a needle | mover, and the magnitude | size of a thrust in the offset linear actuator which concerns on this invention, and the conventional linear actuator which is not offset. It is a longitudinal cross-sectional view which shows the linear actuator which concerns on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the linear actuator which concerns on 3rd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the linear actuator which concerns on 4th Embodiment of this invention. It is a longitudinal cross-sectional view which shows the linear actuator which concerns on 5th Embodiment of this invention. It is a longitudinal cross-sectional view which shows the linear actuator which concerns on 6th Embodiment of this invention.

Explanation of symbols

3 plate wave Ne 11 linear actuator 12 yoke (stator)
13 Mover 14, 15 First permanent magnet (permanent magnet)
16, 17 Second permanent magnet (permanent magnet)
18, 19 Coil 30 Iron piece (iron member)

Claims (6)

A stator formed in a tubular body ;
It has at least one iron member and can be reciprocated in the axial direction of the cylindrical body with respect to the stator so as to be inserted into the stator and exposed outwardly from both end openings of the cylindrical body. A movable element provided,
At least one permanent magnet facing the iron member and having a magnetic pole perpendicular to the reciprocating direction and provided on the stator along the reciprocating direction;
A linear actuator comprising a coil provided on the stator,
The permanent magnet is arranged such that the magnetomotive force is asymmetric with respect to the reciprocating direction of the iron member,
In a state where no current flows in the coil, the iron member is arranged at a reference position that is brought closer to the strong side of the magnetomotive force in the reciprocating direction,
In a state where a current is passed through the coil, the magnetomotive force of the coil cancels the magnetomotive force of the strong side region of the magnetomotive force of the permanent magnet and the weak side region of the magnetomotive force of the permanent magnet. By increasing the magnetomotive force, the magnetomotive force of the weak side region becomes larger than the magnetomotive force of the strong side region.
The linear actuator according to claim 1,
The permanent magnet has a magnetomotive force asymmetrically formed by having a thickness in the magnetic pole direction thick at one end of the reciprocating range of the iron member and a thin configuration at the other end. Characteristic linear actuator. The linear actuator according to claim 1,
The permanent magnet is formed asymmetrically in magnetomotive force by making the material on one end side of the permanent magnet different from the material on the other end side in the axial position of the reciprocating range of the iron member. Characteristic linear actuator. The linear actuator according to claim 1,
The permanent magnet is arranged close to one end side in the axial position of the reciprocating range of the iron member, and is not arranged on the other end side so that the magnetomotive force is formed asymmetrically. Linear actuator. The linear actuator according to any one of claims 1 to 4,
A linear actuator, wherein a gap is provided to make a gap between the permanent magnet on the one end side and the iron member smaller than a gap between the permanent magnet or stator on the other end side and the iron member. A linear actuator according to any one of claims 1 to 5,
A linear actuator characterized in that a surface facing the iron member is flush with a reciprocating direction of the mover.

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