JP4880313B2 - Cylinder type linear actuator - Google Patents

Description

  The present invention relates to a cylinder type linear actuator having a permanent magnet in a moving part and a ring coil in a stator part.

  As this type of cylinder type linear actuator, a movable magnet type actuator as shown in FIG. 8 (see Patent Document 1), a movable magnet type actuator as shown in FIG. 9 (see Patent Document 2), and FIG. Such a linear vibration actuator (see Patent Document 3) has been proposed.

8 and 9, the movable element 100 of the movable magnet actuator includes two permanent magnets 102 and 103 that are magnetized in the axial direction and arranged so that the surfaces having the same polarity face each other, and the two permanent magnets. The armature core 104 is sandwiched between magnets 102 and 103 and a pin 101 for transmitting thrust to the outside. The pin 101 is provided on the end face of the permanent magnet 103.
The stator 200 includes three coils 201, 202, and 203 that are movable inside the mover 100, and a magnetic yoke 204 that is provided on the outer peripheral side of the coils 201, 202, and 203. It is configured. The three coils 201, 202, 203 are connected so that the polarities are alternate.
In FIG. 8, fixed-side soft magnetic bodies 205 and 206 are further provided on both end sides of the three series of coils 201, 202, and 203.

The operating principle of the movable magnet actuator shown in FIGS. 8 and 9 will be described below.
By configuring the mover 100 as described above, the mover 100 is formed with a 3-pole mover magnetic pole aligned in the axial direction with the S, N, and S poles.
The three coils 201, 202, and 203 are arranged so as to interlink with the radial magnetic flux generated from the three magnetic poles. In the upper cross-sectional view of the coil 201 and the coil 203, they face from the front to the back of the page. When a current flows and current is applied so that current flows from the back of the paper to the front in the upper cross-sectional view of the coil 202, a force based on Fleming's left-hand rule is generated, and the mover 100 moves to the right. Generates current thrust. When energized in the opposite direction, the polarity of the coils 201, 202, 203 is reversed, and the moving element 100 generates a current thrust toward the left.
The magnetic yoke 204 is for increasing the magnetic flux density component in the radial direction.
The movable magnet actuator shown in FIG. 8 has three coils 201, 202, and 203 arranged so as to effectively use the magnetic flux, and improves thrust and efficiency.

  In Patent Document 1, the mover core 104 sandwiched between the permanent magnets 102 and 103 has an effect of increasing the magnetic flux density component in the radial direction as compared with the case of only two permanent magnets 102 and 103. is described. However, since the axial lengths of the permanent magnets 102 and 103 are not changed, the distance between the south poles of the mover 100 is increased by the length of the mover core 104. Therefore, it is necessary to change the positions and coil widths of the coils 201, 202, and 203 of the stator 200 accordingly, and the length of the actuator becomes longer. Therefore, the comparison cannot be made under the same conditions. When the mover core 104 is used without changing the distance between the magnetic poles of the mover 100, the axial length of the permanent magnets 102 and 103 is shortened accordingly, and the magnetomotive force of the magnets 102 and 103 is reduced. In some cases, the magnetic flux density component may be small.

In the case of FIG. 8, the thrust at the time of excitation becomes the maximum thrust at the center of the stroke (zero displacement), and the thrust becomes smaller toward the stroke ends on both sides. For this reason, when the load increases, the stroke decreases, and when the load varies, the stroke also varies. In order to solve this problem, the movable magnet actuator shown in FIG. 9 has been proposed.
Since this movable magnet type actuator is provided with fixed-side soft magnetic bodies 205 and 206 on both ends of the three coils 201, 202 and 203, when the moving element 100 moves to the stroke end, When approaching the soft magnetic bodies 205 and 206, a detent force (non-excited attraction force) acts between the mover magnets 102 and 103 and the fixed-side soft magnetic bodies 205 and 206, and the left hand of the framing near the stroke end. The thrust is strengthened so as to compensate for the decrease in the thrust based on the law, the reduction in the stroke when the load increases can be reduced, and the change in the stroke due to the change in the load can also be suppressed.

In the case of the linear vibration actuator shown in FIG. 10, the moving element 300 includes a linear motion shaft 301 that reciprocates in the axial direction, and permanent magnets 302 and 303 that are magnetized so that the surfaces facing each other have the same polarity. Inductors 304, 305, and 306 made of a magnetic material disposed on both axial sides of the permanent magnets 302 and 303, and the permanent magnets 302 and 303 and the inductors 304, 305, and 306 are integrally held and the linear motion shaft 301 is provided with a guide 307 for coupling with 301.
The stator 400 includes a ring-shaped excitation coil 401, stator magnetic poles 402 and 403 disposed on both axial sides of the ring-shaped excitation coil 401, and a stator that magnetically couples the stator magnetic poles 402 and 403. And a yoke 404.

Next, the operation principle of the linear vibration actuator of Patent Document 3 will be described.
In the state shown in FIG. 10, the moving element 300 is at the first non-excitation stable point. At this time, when the exciting coil 401 is excited so that the stator magnetic pole 402 is an N pole and the stator magnetic pole 403 is an S pole, a repulsive force is generated between the inductor 305 and the stator magnetic pole 403, and the inductor 305 and the stator magnetic pole 402 In the meantime, a suction force is generated, and the moving element 400 moves to the left. Then, when the stator magnetic pole 402 and the inductor 305 start to face each other, a non-exciting holding force to be drawn into the second non-excited stable point where the stator magnetic pole 403 and the inductor 306 face each other is added by the action of the taper provided in the inductor 305. The mover 300 reaches the second non-excitation stable point and stops. The moving element 300 can be reciprocated by periodically reversing the direction of the current applied to the exciting coil 401, and a linear vibration actuator can be configured.
JP-A-6-38486 JP-A-8-116658 Japanese Patent Laid-Open No. 11-215794

However, since the movable magnet type actuator shown in FIG. 8 mainly uses the thrust based on Fleming's left-hand rule, the excitation stable point is near the stroke end, and the position can be changed even if the magnitude of the current is changed. Can hardly be changed.
“Thrust decreases as the stroke ends on both sides” means that there is a stable equilibrium point (stable point) on one side and an unstable equilibrium point on the other side.
In other words, even if the magnitude of the current is changed, only the slope of the thrust at the excitation stable point (rigidity = change in thrust against a slight change in position) changes, and it remains stable without changing the thrust slope at the excitation stable point. There was a problem that only the position of the point could not be changed.

In the case of FIG. 9, since the fixed-side soft magnetic bodies 205 and 206 are provided on both ends of the three coils 201, 202, and 203, there are two non-excitation stable points on both ends of the stroke. The two excitation-free stable points can be traversed by exciting the exciting winding. It is difficult to stop halfway, and if the mover 100 slightly deviates from the center, a thrust force that attracts the mover 100 toward the non-excitation stable point in the deviated direction is generated. That is, when the moving element 100 is slightly displaced from the center due to an external force, there is a problem in that the moving element 100 arbitrarily moves to a non-excitation stable point in the shifted direction.
Since the excitation stable point is near the stroke end as in the case of FIG. 8, the current value is adjusted so that the excitation stable point is moved by an amount depending on the current value, and the load cannot be controlled at an arbitrary position. There was also a problem.

Also, the linear vibration actuator shown in FIG. 10 has two non-excitation stable points as in the actuator of FIG. 8, and the two non-excitation stable points are obtained by exciting the excitation coil (excitation winding) 401. You can come and go. It is difficult to stop the operation halfway, and there are problems similar to those shown in FIGS.
Further, since the stator magnetic poles 402 and 403 are used for the stator 400, there is a problem that when the excitation current is increased, the stator magnetic poles 402 and 403 are saturated and the thrust is not proportional to the excitation current.
In addition, it is necessary to devise the shape of the tips of the stator magnetic poles 402 and 403 and the shape of the inductor 305, which causes a cost increase.

The present invention solves the above-mentioned problem, and only controls the current value of one excitation winding, and hardly changes the inclination of the holding force at the excitation stable point, and only depends on the current value of the stable point. It is an object of the present invention to provide a cylinder type linear actuator that can be displaced in a moving manner.
In addition, since there is only one excitation winding, the configuration of the drive circuit is simplified, the actuator structure is simple, and there is provided a cylinder type linear actuator that is free from problems of cost increase and magnetic saturation of the stator poles. Objective.

In order to solve the above problems, the present invention is configured as follows.
A linear motion shaft that is reciprocally movable in the axial direction, and at least one permanent magnet that is provided on the linear motion shaft and is magnetized so as to form a plurality of magnetic poles with a magnetic pole pitch τp along the travel direction. a moving element comprising comprising more pieces, annular arranged around the moving element so interlinked with the radial direction of the magnetic flux generated from the plurality of mover poles formed in the axial direction of the mover A stator having a coil and a yoke member made of a soft magnetic material provided outside the ring-shaped coil , and the non-excited holding force generated by the permanent magnet of the mover and the yoke member is The axial center position of the yoke member is a non-excitation stable point, and a maximum value is generated in the range where the displacement is 0.6τp or less, and the current thrust due to the current flowing through the ring-shaped coil is near the non-excitation stable point. The maximum value It is to be controlled to generate a remote small maximum value.
Further, according to the present invention, when there are a plurality of the ring-shaped coils, each ring-shaped coil is connected so as to generate a current thrust in the same direction when a current is passed through the ring-shaped coil. Is to form.
Further, according to the present invention, the moving element has n cylindrical rare earth magnets magnetized in the moving direction, where n is an integer of 1 or more, and (n + 1) moving element magnetic poles. The yoke member has a cylindrical shape having the same axis as the moving element, and the moving direction length Ly of the yoke member is expressed by Ly = k · n · τp, The inner diameter Dy is expressed by Dy = j × Dm, where Dm is the outer diameter of the rare earth magnet .
In the present invention, the k is set in the range of 1 to 1.5, and the j is set in the range of 1.3 to 1.7.
Furthermore, the present invention lies in that when the moving element n is 2, the yoke member is divided into two at a central portion in the axial direction by a nonmagnetic member or a space.

  According to the present invention, it is possible to generate a non-excitation holding force with the yoke center as a stable point by setting the yoke length optimally. An excitation winding having an excitation stability point that is different from the non-excitation stability point and generating an excitation holding force having a maximum value smaller than the maximum value of the non-excitation holding force is provided. By controlling the current value, the non-excitation holding force can be displaced by an amount corresponding to the current value.

  Therefore, only by controlling the current value of one excitation winding, it is possible to change only the stable point depending on the current value without changing the inclination of the holding force at the excitation stable point. A linear actuator can be constructed and can be positioned at any position within the stroke range.

  Further, since only one exciting winding is required, the number of necessary switching elements is four, and the control circuit can be constructed at low cost. Since no stator magnetic poles are required, there is no problem of magnetic saturation and the structure is simple, so that a cylinder type linear actuator can be constructed at low cost. It can also be operated as a vibration actuator by passing a variable frequency current through the excitation winding.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of the present invention, and FIG. 2 is a diagram showing an axial distribution waveform of a radial component of magnetic flux density by a moving element of the present invention and a permanent magnet assembly corresponding thereto.

  1 and 2, a moving element 10 is brought into contact with a linear motion shaft 11 that reciprocates in the axial direction, a permanent magnet 12 that is magnetized in the axial direction as shown, and both end faces of the permanent magnet 12. And a mover assembly 17 composed of mover iron cores 14 and 15 disposed. The mover 10 includes at least one permanent magnet 12 magnetized so as to form a plurality of mover magnetic poles at a magnetic pole pitch τp along the moving direction.

Normally, the mover cores 14 and 15 are used to achieve a desired distance between magnetic poles while using a minimum number of permanent magnets. When the mover cores 14 and 15 are not present, the center position of the mover magnetic pole is near the positions of both end faces of the permanent magnet 12, and when the mover cores 14 and 15 are present, the center position is near the center of the mover cores 14 and 15. .
The permanent magnet assembly 17 is firmly fixed to the linear motion shaft 11 by fixing ring members 18 and 19 disposed at both ends thereof. The moving element 10 is housed in the case 30 and is supported so as to be movable in the axial direction via bearings 33 and 34 disposed at the centers of a pair of brackets 31 and 32 facing each other at a predetermined interval. .

On the other hand, the stator 20 includes a cylindrical yoke (yoke member) 21 made of a soft magnetic material fixed to the inner peripheral surface of the case 30, and a ring shape disposed on the inner peripheral surface side of the cylindrical yoke 21. The coils 22 and 23 are used. Normally, the length of the cylindrical yoke 21 in the axial direction is such that the slider 10 generates an appropriate non-excitation holding force with the axial center position of the cylindrical yoke 21 as the non-excitation stable point. It is set slightly longer than the distance between 10 magnetic poles.
That is, when the axial length of the permanent magnet 12 is Lm and the axial length of the mover cores 14 and 15 is La, the axial length Ly of the yoke member 21 is Ly = k (Lm + La). The constant k is set in the range of 1 to 1.5. In the case where the mover cores 14 and 15 are not provided, Ly = k · Lm.
The ring-shaped coils 22 and 23 are arranged at positions almost opposite to the magnetic pole of the moving element 10 when the moving element 10 is at the non-excitation stable point, and are connected so that the polarities are reversed when energized. Has been.

  The moving element 10 has n cylindrical rare earth magnets magnetized in the moving direction to form (n + 1) moving element magnetic poles, where n is an integer of 1 or more. . The cylindrical yoke 21 has a cylindrical shape having the same axis as that of the moving element 10. The moving direction length Ly of the cylindrical yoke 21 is expressed by Ly = k · n · τp, and k is 1 To 1.5, and the inner diameter Dy of the cylindrical yoke 21 is expressed as Dy = j × Dm, where Dm is the outer diameter of the rare earth magnet, and j is from 1.3 The range is set to 1.7.

Next, the operation of the above embodiment will be described.
The excitation stable point of the holding force during excitation caused by the current of the excitation winding is slightly outside the center position of the ring coils 22 and 23, and is generated at a position different from the non-excitation stable point.
This means that the vectors of the non-excitation holding force and the excitation holding force have a certain angle, and the combined vector of the two vectors means that the angle changes depending on the magnitude of the excitation holding force vector. The non-excitation holding force generated by the permanent magnet 12 of the moving element 10 and the cylindrical yoke 21 is maximum when the axial center position of the cylindrical yoke 21 is a non-excitation stable point and the displacement is 0.6 τp or less. And the current thrust caused by the current flowing through the ring-shaped coils 22 and 23 is controlled to generate a maximum value smaller than the maximum value near the non-excitation stable point.

FIG. 6 shows the relationship between the non-excitation holding force and the holding force during excitation.
By appropriately setting the length of the cylindrical yoke 21, a non-excited holding force having a maximum value larger than the maximum value of the current-induced holding force and having a stable point at the center of the yoke is generated as shown in the figure.
When the value is positive, it means that the thrust in the positive direction works, and when it is negative, the thrust in the negative direction works. Therefore, a point where the slope of the holding force curve at the zero cross point is negative is a stable equilibrium point (stable point), and a positive point means an unstable equilibrium point.

Here, in the upper cross-sectional view of the ring-shaped coil 22, current flows from the back to the front of the paper, and in the upper cross-sectional view of the ring-shaped coil 23, when current is passed so as to flow from the front to the back of the paper, The holding force due to the current is like the current-induced holding force A.
The excitation stable point at that time is the zero cross point on the right side of the figure.
As a result, the combined holding force when energized is the combined holding force A, and the non-excited holding force has a waveform shifted to the right.

When energized in the opposite direction, the current-induced holding force becomes the current-induced holding force B. As a result, the combined holding force at the time of energization becomes the combined holding force B, and the non-excited holding force is The waveform is shifted to the left.
When a current value is set between the two current values, the combined holding force is naturally between the combined holding force A and the combined holding force B.
From this, it can be seen that by controlling only the current value of the excitation winding, only the stable point can be displaced depending on the current value without changing the inclination of the holding force at the excitation stable point.

The magnitude and wave shape of the non-excitation holding force generated by the permanent magnet 12 and the cylindrical yoke 21 of the moving element 10 are determined by the dimensions of the moving element 10, the dimensions of the cylindrical yoke 21, and the material of the permanent magnet 12. Come.
In order to solve the above problem, the inclination of the non-excitation holding force at the excitation stable point, that is, the rigidity is increased, and the current thrust caused by the current is the maximum of the non-excitation holding force near the non-excitation stable point. It is necessary to arrange the coils 22 and 23 so as to generate a maximum value smaller than the value and to control the current value.
Furthermore, it is necessary to make the cycle of the non-excitation holding force shorter than the cycle of the current thrust.

  FIG. 6 shows this state, and the maximum value of the current thrust when a continuous rated current determined by the allowable loss is applied is less than 40% of the maximum value of the non-excitation holding force at the non-excitation stable point. Is set.

  The displacement at which the current thrust becomes zero is around 0.6τp, which corresponds to 90 degrees when the current thrust waveform is assumed to be a cosine wave. Degree) is 2.4τp. The non-excitation holding force is the case where k = 1.3 in FIG. 7, and the displacement for generating the maximum value of the non-excitation holding force is 0.4τp.

Therefore, the one period in this case is 1.6τp, and the non-exciting holding force from FIG. 7 of the current thrust is the non-excited stable point at the axial center position of the cylindrical yoke 21 (the origin in FIG. 7). (= k · τp) it can be seen that it is possible to vary the displacement for generating a maximum value by varying the. Here, the magnetic pole pitch τp of the mover is 30 mm. If the displacement that generates the maximum value is too large, the slope (rigidity) of the non-exciting holding force at the stable point becomes small and unsuitable for positioning applications. Therefore, the displacement that generates the maximum value is 0.6τp. the following range of good or properly, in the present embodiment is set to 0.4Taupi.

It can be seen from FIG. 7 that if the value of k is set to 1.5 or less, the displacement can be made 0.6τp or less. However, when k is less than 1, the maximum value of the non-excitation holding force is also reduced, so that the range of 1 to 1.5 can be said to be the optimum value for k.

Next, FIGS. 3, 4 and 5 show other embodiments of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the same parts will be omitted.
FIG. 3 and FIG. 4 are examples of a cylinder-type linear actuator having a moving element having two permanent magnets arranged so that surfaces having the same polarity face each other.

  3 and 4, the moving element 10 is in contact with two permanent magnets 12 and 13 arranged so that the surfaces having the same polarity face each other, and the outer end faces of the permanent magnets 12 and 13, and is axially long. Is provided between the two permanent magnets 12 and 13, and the movable iron core 15 having an axial length Lb. The roles of the mover cores 14, 15, 16 are as described above, and may not be used at all, or only the mover core 15 may be used.

The stator 20 includes a cylindrical yoke 21 made of a soft magnetic material fixed to the case 30 and ring-shaped coils 22, 23 and 24. Of course, there is no problem even if only the ring-shaped coil 23 is used in order to shorten the axial length of the actuator.
The length of the cylindrical yoke 21 in the axial direction is usually that of the moving element 10 so as to generate an appropriate non-excitation holding force with the axial center position of the cylindrical yoke 21 as a non-excitation stable point. It is set slightly longer than the distance between the magnetic poles at both ends. That is, as shown in FIG. 5, the axial lengths of the permanent magnets 12 and 13 are Lm, the axial lengths of the mover cores 14 and 16 located on both ends of the permanent magnet assembly 17 are La, and the permanent When the axial length of the mover core 15 positioned between the magnets 12 and 13 is Lb, the axial length Ly of the yoke member is expressed as Ly = k (2Lm + La + Lb), and the constant k is It is set in the range of 1 to 1.5.
In this case as well, if there are no movable cores 14 and 16 on both ends, Ly = k (2Lm + Lb).

Further, the ring-shaped coils 22, 23, and 24 are arranged at positions that oppose the moving pole of the moving element 10 in the radial direction, that is, in the radial direction when the moving element 10 is at the non-excitation stable point. Are connected so that their polarities are opposite to each other.
The excitation stable point of the holding force at the time of excitation caused by the current of the excitation winding is near the reversal point of the magnetic pole of the slider when the slider 10 is at the non-excitation stable point, that is, at a position different from the non-excitation stable point. appear.
This means that the vectors of the non-excitation holding force and the excitation holding force have a certain angle, and the combined vector of the two vectors means that the angle changes depending on the magnitude of the excitation holding force vector.

  The non-excitation holding force in the case of FIG. 3 depends on the magnetic flux of the magnetic poles at both ends of the moving element 10 and does not depend on the magnetic flux of the magnetic poles at the center of the moving element 10. Therefore, the non-excitation holding force has almost the same value as in the case of FIG. 1 configured with one permanent magnet. However, since the current-induced holding force by the ring-shaped coil 23 depends on the magnetic flux of the magnetic pole at the center of the moving element 10, a larger holding force can be generated than in the case of FIG. As a result, the shift amount of the combined holding force can be made larger than in the case of FIG.

  The embodiment of FIG. 4 is a modification of the yoke 21 of the embodiment of FIG. 3, and is divided into two by a nonmagnetic member or a gap 25 at the central portion in the axial direction of the yoke 21. By doing so, the magnetic flux of the magnetic pole at the center of the moving element 10 is also involved in the non-excitation holding force, and the non-excitation holding force can be made larger than in the case of FIG. The other configuration is the same as that of FIG.

According to the above embodiment, the following effects can be obtained.
By setting the length of the cylindrical yoke 21 optimally, a non-excitation holding force with the center of the cylindrical yoke 21 as a stable point can be generated. Two or three rings are used as excitation windings that have excitation stable points different from the non-excitation stable points and generate excitation holding force having a maximum value smaller than the maximum value of the non-excitation holding force. By providing the coil-like coils 22, 23 and 24 and controlling the current value of the excitation winding, the non-excitation holding force can be displaced by an amount corresponding to the current value.

  Therefore, only by controlling the current value of one excitation winding, it is possible to change only the stable point depending on the current value without changing the inclination of the holding force at the excitation stable point. A linear actuator can be constructed and can be positioned at any position within the stroke range.

  Further, since only one excitation winding is required, the number of necessary switching elements is four and the control circuit can be configured at low cost. Since no stator magnetic poles are required, there is no problem of magnetic saturation and the structure is simple, so that a cylinder type linear actuator can be constructed at low cost. It can also be operated as a vibration actuator by passing a variable frequency current through the excitation winding.

  Note that the present invention is not limited to the above-described embodiment. In the above-described embodiment, when the number of permanent magnets constituting the mover assembly 17 is one, two ring-shaped coils 22 and 23 are used. In the case of two permanent magnets, three ring coils 22, 23, 24 are used. For example, in the case of four permanent magnets, the ring assembly is formed using five ring coils. It can also be configured. Also, the cylindrical yoke 21 can be divided into a plurality of parts depending on the number of permanent magnets. In addition, the present invention can be implemented with appropriate modifications without departing from the scope of the present invention.

It is sectional drawing which shows embodiment of the cylinder type linear actuator of this invention. It is the figure which showed the axial direction distribution waveform of the radial direction component of the magnetic flux density by the movable element of this invention, and the permanent magnet assembly corresponding to it. It is sectional drawing which shows other embodiment of the cylinder type linear actuator of this invention. It is sectional drawing which shows other embodiment of the cylinder type linear actuator of this invention. It is the figure which showed the axial direction distribution waveform of the radial direction component of the magnetic flux density by the permanent magnet assembly corresponding to the slider of FIG. 3, FIG. It is a figure which shows the relationship between the non-excitation holding force and the holding force at the time of excitation. It is a figure which shows a non-excitation holding force characteristic. It is sectional drawing which shows the conventional movable magnet type actuator. It is sectional drawing which shows the conventional movable magnet type actuator. It is sectional drawing which shows the conventional linear vibration actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mover 11 Linear motion shaft 12, 13 Permanent magnet 14, 15, 16 Mover iron core 17 Mover assembly 18, 19 Fixed ring member 20 Stator 21 Cylindrical yoke 22, 23, 24 Ring coil 30 Case 31, 32 Bracket

Claims (5)

A linear motion shaft provided so as to be capable of reciprocating in the axial direction, and provided on the linear motion shaft,
A moving element comprising a magnetized permanent magnet so as to form a plurality of moving element pole comprises at least one or more magnetic pole pitch τp along the movement direction,
A ring-shaped coil disposed around the slider so as to interlink with a radial magnetic flux generated from a plurality of slider magnetic poles formed in the axial direction of the slider;
A stator having a yoke member made of a soft magnetic material provided on the outside of the ring-shaped coil, and the non-exciting holding force generated by the permanent magnet of the mover and the yoke member is the yoke member Is the non-excitation stable point, the maximum value is generated in the range where the displacement is 0.6τp or less, and the current thrust due to the current flowing through the ring coil is the maximum near the non-excitation stable point. A cylinder-type linear actuator controlled to generate a maximum value smaller than the value .   When there are a plurality of the ring-shaped coils, each ring-shaped coil is connected so as to generate a current thrust in the same direction when a current is passed through the ring-shaped coil to form one excitation winding. The cylinder-type linear actuator according to claim 1. The moving element has n cylindrical rare earth magnets magnetized in the moving direction to form (n + 1) moving element magnetic poles, where n is an integer of 1 or more, The yoke member has a cylindrical shape having the same axis as the moving element, and the moving direction length Ly of the yoke member is expressed by Ly = k · n · τp,
3. The cylinder type linear actuator according to claim 1, wherein an inner diameter Dy of the yoke member is expressed by Dy = j × Dm, where Dm is an outer diameter of the rare earth magnet . The cylinder type linear actuator according to claim 3, wherein k is set in a range of 1 to 1.5, and j is set in a range of 1.3 to 1.7. . 5. The cylinder type according to claim 3, wherein, when n is 2, the yoke member is divided into two at a central portion in the axial direction by a nonmagnetic member or a space. Linear actuator.

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