JPH10225082A - Linear solenoid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear solenoid which can be retained well at a prescribed neutral position at the time of shutting off energizing, without using a return spring, and is capable of making a displacement in proportion to energizing amount and direction from the neutral position to an arbitrary fore or aft direction according to the energizing amount and direction. SOLUTION: A plunger 10 is retained at an energizing 0 position, where the central part of a permanent pole face 120 and a neck part 211 overlap each other in an axial direction at the time of shutting off energizing (non- energizing). When an electric current is carried in an exciting coil 23 in a prescribed direction, attraction and repulsion act between the permanent pole face 120 of the plunger 10, and both the pole piece parts 213 of an inner yoke 21, and axial thrust is generated by the forces. The plunger 10 is deviated almost linearly, corresponding to energizing amount by the axial thrust, so that the direction of the axial thrust is reversed by the change in the energizing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet movable linear solenoid in which a permanent magnet forming a permanent magnetic pole surface is disposed on a plunger (hereinafter, also simply referred to as "linear solenoid").

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 7-274468 discloses that a plunger made of a permanent magnet is slidably fitted in a drive coil, and both ends of the plunger are made permanent magnet poles of opposite polarities. A linear solenoid that drives a plunger in an axial direction by a formed magnetic field is disclosed. The magnetic pole faces (permanent magnetic pole faces) of these permanent magnetic pole portions mainly consist of both end faces of a cylindrical plunger.

[0003] In addition, conventionally known linear solenoids or solenoid valves with return springs are also widely known. These solenoids with return springs have a core that forms a magnetic circuit with a gap, and when energized to the exciting coil, a plunger made of a magnetic material moves directly in the axial direction so that the gap is magnetically short-circuited. When the power is cut off, the gap is magnetically opened by the return spring to move directly to the opposite side in the axial direction.

[0004]

However, the linear solenoid disclosed in the above-mentioned publication has a problem that the position of the plunger at the time of energization cutoff cannot be clearly defined. Further, in the solenoid with the return spring, although the plunger position at the time of energization cutoff can be clearly specified by the return spring, it is difficult to realize a thrust (driving force), that is, a proportional relationship between the amount of current and the displacement of the plunger. There is a problem that high-precision control is difficult. In addition, it is not easy to drive the plunger in the opposite direction from the power-cutting position by reversing the current-flowing direction because of using a return spring. In addition, there is a problem that the structure is complicated by the amount of the return spring.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is satisfactorily held at a predetermined neutral position when power is cut off without using a return spring. It is an object of the present invention to provide a linear solenoid that can be displaced in any direction before and after in proportion to the amount of current flow and the direction of current flow.

[0006]

According to the linear solenoid of the present invention, a plurality of ring cores are sequentially arranged in the axial direction. Each ring core is provided with a pair of magnetic pole pieces on both sides in the axial direction with respect to the neck portion where the magnetic resistance is maximized, and has a ring-shaped cross section in the axial direction. A pair of ring cores adjacent in the axial direction are magnetically connected by a yoke disposed at a position distant from the plunger, and a magnetic flux by the permanent magnet is transmitted to the first outer peripheral surface of the plunger, the air gap, the first ring core. , A yoke, a second ring core, an air gap, and a gap magnetic circuit that sequentially passes through the second outer peripheral surface of the plunger. Therefore, both end surfaces of the plunger are magnetic pole surfaces having opposite polarities (hereinafter, also referred to as permanent magnetic pole surfaces).

Hereinafter, the operation of the linear solenoid will be briefly described. When power is cut off (when power is not supplied), the plunger is positioned at the position where the air gap length between the ring core and the permanent magnetic pole face facing the ring core is minimum, that is, the center of the permanent magnetic pole face and the neck of the ring core. It is held at the energized zero position that overlaps in the axial direction. Accordingly, an axial thrust (hereinafter also referred to as a return thrust or a self-spring force) acting on the plunger to be returned to the energized zero position by being urged by the permanent magnet when the energization is cut off acts on the plunger.

On the other hand, when the exciting coil is energized in a predetermined direction, an exciting magnetic flux penetrating through the ring core is formed. The neck portion is formed to have the highest reluctance as compared with other portions of the ring core, so that a part or most of the exciting magnetic flux is directed outward from the surface of the pole pieces on both sides of the neck portion. The surfaces of the magnetic pole pieces on both sides of the neck, especially the surfaces of the two magnetic pole pieces near the neck, have magnetic pole surfaces (exciting magnetic pole surfaces) of opposite polarities.

As a result, an attractive force acts between the permanent magnetic pole face of the plunger and one of the two exciting magnetic pole faces, and a repulsive force acts between the permanent magnetic pole face of the plunger and the other of the two exciting magnetic pole faces. Working, these forces produce axial thrust. As the energizing current increases, the magnetic center position of the attracting-side exciting pole surface (of the opposite polarity to the permanent magnetic pole surface) moves away from the neck in the axial direction due to the increase in the amount of leakage magnetic flux, and the central portion of the permanent magnetic pole surface An axial thrust (hereinafter also referred to as a suction thrust) acts so as to be displaced accordingly. In addition, when the amount of supplied current is increased, the repulsive force between the exciting magnetic pole surface on the repulsive side (having the same polarity as the permanent magnetic pole surface) and the permanent magnetic pole surface increases, so that the permanent magnetic pole surface moves away from the repulsive exciting magnetic pole surface. Axial thrust (hereinafter also referred to as repulsive thrust) acts on the permanent magnetic pole surface as far as possible.

As described above, the return thrust and the repulsive thrust become weaker as the plunger is displaced, resulting in forces in opposite directions, and the repulsive thrust increases according to the amount of current. The suction thrust has a predetermined maximum displacement position.
Since these action mechanisms and the permanent magnetic pole surface have a shape that gradually separates from the ring core as they move away from the center, and both excitation magnetic pole surfaces have a shape that gradually separates from the excitation magnetic pole surface as they move away from the neck, Accordingly, the plunger is displaced substantially linearly, and by adjusting the shapes of the exciting magnetic pole surface and the permanent magnetic pole surface and the cross-sectional shape of both magnetic pole pieces, the amount of current flowing and the amount of displacement of the plunger can be made highly accurate. Since a pair of ring cores adjacent in the axial direction across the permanent magnet of the plunger are excited in opposite directions, the axial thrust between these two ring cores and the pair of permanent magnetic pole faces individually facing each other is In the same direction, the combined axial thrust is doubled.

However, in the above description, the magnetic charge density of the excitation magnetic pole surface and the magnetic charge density of the permanent magnetic pole surface, in other words, the strength of these two magnetic poles changes according to the amount of current flowing. The operation and effect of the present invention described above will be described below. According to the present invention, the plunger can be returned to the predetermined energized zero position when the energization is cut off, the plunger can be driven in the opposite direction by changing the energization direction, and the plunger displacement is continuously changed by the change in the energization amount. In addition, a highly accurate linear solenoid can be realized with a simple configuration without using a mechanical spring or the like.

According to the second aspect, the plunger is made of a soft magnetic material which is individually joined to both ends in the axial direction of the permanent magnet and whose outer peripheral surface forms a permanent magnetic pole surface. If you do this,
The leakage of the exciting magnetic flux from the pole piece of the ring core during energization is favorably absorbed by the soft magnetic material of the plunger, so that the axial thrust is strengthened.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ring core is made of a soft magnetic material. The neck of the ring core may be an air gap. The plunger has a pair of permanent magnetic pole faces on both sides in the axial direction with a permanent magnet interposed therebetween, but it is also possible to form three or more permanent magnetic pole faces in the axial direction.

The cross section in the direction perpendicular to the axis of the ring core may be cylindrical, but is not limited to this, and may be various shapes such as a cylindrical shape having a rectangular cross section. In a preferred embodiment, the distance between the pole piece and the axis is formed to increase at an increasing rate as the distance from the neck in the axial direction increases. This makes it possible to increase the accuracy of the proportional relationship between the current amount and the displacement amount.

In a preferred embodiment, the distance between the permanent magnetic pole surface of the plunger and the axis is formed to increase at an increasing rate as the distance from the axial center of the permanent magnetic pole surface increases in the axial direction. This makes it possible to increase the accuracy of the proportional relationship between the current amount and the displacement amount.

[0016]

【Example】

(Embodiment 1) An embodiment of a linear solenoid according to the present invention will be described below with reference to FIG. The linear solenoid includes a plunger 10, a stator 20, and a bearing member 3.
0.

The plunger 10 has a cylindrical permanent magnet 1.
1 and a pair of cylindrical magnetic pole pieces 12 made of a soft magnetic material individually fixed to both end faces of the permanent magnet 11. The output shaft 13 is fitted and fixed to the permanent magnet 11 and the magnetic pole pieces 12. I have. Both end surfaces of the permanent magnet 11 are magnetized to the N and S poles. As a result, the outer peripheral surfaces 120 of both pole pieces 12 are magnetized to the N pole or the S pole to become permanent magnetic pole surfaces. The outer peripheral surface 120 has a shape in which the center portion in the axial direction has the largest diameter and the both end portions have the smallest diameters, and has a shape (so-called spindle shape) in which the diameter decreases at an increasing distance from the center portion in the axial direction.
Is formed.

The stator 20 includes a cylindrical inner yoke 21, an outer yoke 22, and a pair of excitation coils 23, each of which is made of a soft magnetic material. Inner yoke 21
Is a pair of coil housing grooves 2 annularly recessed radially inward.
10, both coil accommodating groove portions 210 are formed at a predetermined pitch in the axial direction. The axially central portion of the coil housing groove 210 forms a neck portion 211 having the smallest diameter, and the thickness of the inner yoke 21 in the neck portion 211 is minimized. The inner yoke 21 includes a cylindrical portion 212 having a large diameter, and a magnetic pole piece portion 213 having an inner peripheral surface and an outer peripheral surface that are gradually reduced in diameter from the cylindrical portion 212 to the neck portion 211 along the coil housing groove 210. Consists of The inner peripheral surface of the cylindrical portion 212 has a large diameter at the center in the axial direction and small diameters at both ends. The pole piece portions 213 are formed on both sides in the axial direction with the neck portion 211 interposed therebetween. The inner peripheral surface of the pole piece 213 has such a shape that the diameter increases at an increasing rate as the distance from the neck 211 increases.
The outer peripheral surface of the pole piece 213 has a shape whose diameter increases linearly as the distance from the neck 211 increases. As a result, the axial section of the coil receiving groove 210 has a triangular shape, the thickness of the pole piece 213 increases as the distance from the neck 211 increases, and the inner peripheral surface of the inner yoke 21 It has a waveform shape as a whole.

The bobbin 23 is inserted into the coil receiving groove 210.
The excitation coil 23 wound around 0 is housed, and then the outer yoke 22 made of a soft magnetic material shields both coil housing grooves 210. As a result, the ring core according to the present invention includes the neck portion 211 of the inner yoke 21, the pair of magnetic pole pieces 213 on both sides thereof, and the outer yoke 22, and the cylindrical portion 212 of the inner yoke 21 is the yoke referred to in the present invention. Is composed.

The bearing member 30 has a pair of end plates 31, a pair of holders 32, and a pair of bearings 33. After the inner yoke 21 has the pair of outer yokes 22 fitted therein, the inner yoke 21 has a pair of end plates. The end plate 31 is assembled by fastening the end plates 31 with through bolts (not shown). The two bearings 33 held by the holder 32 hold the output shaft 13 for a week.

The axial distance between the two neck portions 211 is set to be equal to the distance between the axial center portions of the two pole pieces 12 of the plunger 10. Hereinafter, the operation of this linear solenoid will be described. Both pole pieces 12 of plunger 10
The outer peripheral surface 120 is magnetized by the permanent magnet 11 to be a permanent magnetic pole surface, and the magnetic flux of the permanent magnet 11 is
Magnetic pole surface 120, a pair of magnetic pole piece portions 213 of the inner yoke 21, and a large-diameter cylindrical portion 21 of the inner yoke 21
2. Another pair of pole pieces 213 of the inner yoke 21;
A gap magnetic circuit is formed that flows through the permanent pole face 120 of the other pole piece 12.

Therefore, at the time of de-energization (when not energized), the position where the average gap length is minimum, ie,
The central portion in the axial direction of the permanent magnetic pole surface 120 and the neck portion 211 are urged toward a position (origin position) where they coincide with each other in the axial direction. Next, both excitation coils 23 are energized, and the inner peripheral surfaces of the pair of magnetic pole pieces 213 on the outside in the axial direction become one polarity,
Excitation is performed so that the inner peripheral surfaces of the pair of pole pieces 213 on the inner side in the axial direction have the other polarity. Then, the permanent magnetic pole face 120
Is displaced to the axial position where the above-described suction thrust, repulsion thrust and return thrust are balanced. When the amount of current is changed, the balance position is continuously changed accordingly, and when the direction of current is changed, the displacement direction of the plunger 10 is changed.

Therefore, according to the linear solenoid of this embodiment, without using a return spring, it is satisfactorily held at the predetermined neutral position when the power is cut off. A linear solenoid that can be displaced in the direction in proportion to the amount of current flowing and the direction of current flow can be realized. In addition, the excitation coil 23
The excitation magnetic flux formed by energizing the magnetic pole piece and forming the excitation magnetic pole surface on the inner peripheral surface of the pole piece portion 213 bypasses the neck portion 211 and passes through the pole piece 12 of the plunger 10 satisfactorily. The amount of exciting magnetic flux can be increased by shortening the air gap length of the magnetic circuit of the magnetic flux, and the axial thrust can be increased.

Hereinafter, the operation of the linear solenoid will be described in more detail. (When not energized) The plunger position shown in FIG. 1 is in the state where the magnetic flux (magnetic energy) is flowing the most, and if the plunger is moved from this position to the left or right (x direction), the change in the magnetic flux is either way. Since the value is negative, within a predetermined stroke range, a restoring force for returning to the original position is generated, and the relationship between the restoring force and the stroke has a characteristic shown in FIG. FIG. 3 shows the flow of the magnetic flux immediately after the energizing of the exciting coil 23 (before the movement).

The magnetic flux flowing through the magnetic pole piece 213 on the left side of the neck portion 211 is obtained by adding the magnetic flux of the permanent magnet 11 and the magnetic flux generated by the exciting coil 23. The value obtained by subtracting the magnetic flux by the excitation coil 23 from the magnetic flux of the excitation coil 23 is obtained. For example,
As shown in FIG. 4, the pole piece 2 on the left side of the neck 211
13, the magnetic flux flowing through the pole piece 213 on the right side of the neck 211 becomes zero.

In this state, the magnetic flux moves to the left to the point where the magnetic flux becomes maximum, and is balanced at the position shown in FIG. Plunger 1
If you try to move 0 further left from this equilibrium position,
This time, since the magnetic path length of the air gap increases and the magnetic flux decreases, the plunger 10 equilibrates at a position displaced by a predetermined distance. FIG. 6 shows the relationship between the current flowing amount I and the displacement amount x.
Shown in When the amount of current I is increased, FIG.
Since the characteristic line shown in (1) slides up and down by the change in the axial thrust corresponding to the change in the flowing current I, the force (total axial thrust) on the characteristic line corresponding to the value of each flowing current I is zero. Plunger 1 up to stroke position
It can be seen that 0 is displaced. Force and stroke x shown in FIG.
FIG. 6 is a diagram in which the relationship between the current I and the stroke x is rewritten. (Temperature Characteristics) Next, the temperature characteristics of the linear solenoid will be described with reference to FIGS.

7 and 8, the thrust characteristics at normal temperature (simulation results) are indicated by solid lines, and the characteristics at high temperatures are indicated by broken lines. It can be seen that the inclination at room temperature is relatively steep, and the parallel movement is substantially proportional to the product of the amount of current (ampere turn) and the strength of the permanent magnet 11 based on the characteristics at the time of non-excitation. The inclination at a high temperature is moderated by the high temperature demagnetization of the permanent magnet 11. This also moves in parallel with the product of the energized AT and the strength of the permanent magnet 11 based on the non-excitation characteristic. FIG. 8 is an enlarged view of the characteristics in the case of no excitation in FIG. 7 and the case where the ampere turn is AT1. (Explanation of normal temperature characteristics) The stroke when the motor is excited at the ampere turn AT1 at normal temperature is determined as follows. First,
Assuming that the increase in thrust at stroke 0 is Fo, the spring characteristics translate in parallel with the magnetic spring characteristics when not excited.

F = −Ko · x + Fo Here, Ko is a spring constant at normal temperature and is proportional to the strength (magnetic flux amount φo) of the permanent magnet 11, so that Ko = K1 · φo. Fo is a bias component due to excitation and is proportional to the strength (magnetic flux amount φo) and the current (I) of the permanent magnet 11, so that Fo = K2 · φo · I. Since the equilibrium point stroke x is F = 0, from the above equation, Fx = Fo / Ko = K2.phi.o / I / (K1.phi.o) = K
・ I However, K = K2 / K1. (Explanation of High-Temperature Characteristics) Next, a stroke when the ampere turn AT1 is excited at a high temperature will be considered. First, assuming that the increase in thrust at stroke 0 is Fh, the spring characteristic F is expressed as F =
−Kh · x + Fh. Here, Kh is a spring constant at a high temperature and is proportional to the strength (excitation amount φh) of the permanent magnet 11, so that Kh = K1 · φh. Fh is a bias component due to excitation and is proportional to the strength (magnetic flux amount φh) of the permanent magnet 11 and the current (I), so that Fh = K2 · φh · I. Since the equilibrium point stroke x1 ′ is F = 0, from the above equation, x1 ′ = Fh / Kh = K2 · φh · I / (K1 · φh) =
K · I. As described above, the stroke x can be represented by an expression irrelevant to the magnetic flux amount φ, so that a characteristic is obtained in which the equilibrium stroke does not change even when demagnetized due to high temperature.

FIG. 9 shows the relationship between the stroke and the ampere turn AT. It is understood that the characteristics do not shift due to the temperature change. (Other Embodiment) Another embodiment of the linear solenoid of the present invention will be described with reference to FIG. In the linear solenoid of this embodiment, the inner yoke 21 of the linear solenoid of the first embodiment shown in FIG. 1 is divided into two parts at the center in the axial direction to be changed to inner yokes 21a and 21b. The yoke 22a is replaced with the inner yoke 21a, 21b and the outer yoke 2a.
2a and a center yoke 28 made of a ring-shaped magnetic material
And the side yoke 29, and the exciting coil 23
To the outer yoke 22a and the center yoke 28, respectively.
And a coil housing groove surrounded by a side yoke 29 and having a rectangular cross section.

This makes it possible to increase the cross-sectional area of the exciting coil 23.

[Brief description of the drawings]

FIG. 1 is an axial sectional view showing one embodiment of a linear solenoid of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a return thrust and a stroke (displacement amount) during non-excitation.

FIG. 3 is a diagram showing a flow of a magnetic flux after energization and before displacement in the linear solenoid of FIG. 1;

FIG. 4 is a diagram showing a flow of magnetic flux after a predetermined stroke displacement after energization in the linear solenoid of FIG. 1;

FIG. 5 is a characteristic diagram showing a relationship between a combined thrust and a stroke when the energizing ampere turn is changed in the linear solenoid having the characteristic of FIG.

FIG. 6 is a characteristic diagram showing a relationship between a current flowing amount and a stroke in the linear solenoid having the characteristic shown in FIG. 5;

FIG. 7 is a characteristic diagram showing a relationship between an energized ampere-turn at normal temperature and a high temperature, a combined thrust, and a stroke.

FIG. 8 is a characteristic diagram showing a relationship between a combined thrust and a stroke at a normal temperature and a high temperature when no excitation is performed and when a predetermined current is applied.

FIG. 9 is a characteristic diagram showing the relationship between the amount of supplied current (ampere turn) and the stroke at normal temperature and high temperature, and both characteristics are illustrated as a single characteristic line, which is completely overlapped.

FIG. 10 is an axial sectional view showing another embodiment of the linear solenoid of the present invention.

[Explanation of symbols]

10 is a plunger, 11 is a permanent magnet, 22 is an outer yoke (the rest of the ring core) 23 is an exciting coil, 120 is a magnetic pole surface (permanent magnetic pole surface) of the plunger 10, 211 is a neck portion of the inner yoke 21 (part of the ring core). Reference numeral 212 denotes a cylindrical portion (yoke) of the inner yoke 21, and reference numeral 213 denotes a magnetic pole piece (a part of a ring core) of the inner yoke 21.

Claims (2)

[Claims] 1. A plurality of ring cores, each having a pair of pole piece portions formed on both sides in the axial direction with a neck portion having a maximum magnetic resistance therebetween and arranged in the axial direction, and wound around the ring core. An excitation coil that magnetizes a pair of adjacent ring cores in opposite directions by energization, and a permanent magnet that forms a magnetic pole surface individually on the outer peripheral surface in the vicinity of each of the neck portions and is slidable in the axial direction. A plunger to be disposed, a yoke that magnetically connects the pair of adjacent ring cores to form a magnetic circuit with a gap with both the ring cores and the plunger, and each of the magnetic pole piece portions includes:
It has a shape that gradually moves away from the magnetic pole surface of the plunger as it moves away from the neck portion, and the magnetic pole surfaces of the plunger move away from the axial center closest to the ring core side when the excitation coil is not energized. A linear solenoid having a shape that gradually moves away from the ring core, wherein an axial pitch of the two pole faces of the plunger is set equal to an axial pitch of the adjacent neck portion. 2. The linear solenoid according to claim 1, wherein the plunger has a soft magnetic body which is individually joined to both ends of the permanent magnet in the axial direction and whose outer peripheral surface forms the magnetic pole surface. Linear solenoid.