CN217157855U

CN217157855U - Solenoid actuator

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Publication number: CN217157855U
Application number: CN202122237030.2U
Authority: CN
Inventors: 张致豪
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2022-08-09
Anticipated expiration: 2031-09-15

Abstract

The utility model discloses a solenoid actuator, which comprises a shell, wherein a coil is arranged in the shell, a hollow channel is formed in the center of the coil, a mandrel is movably arranged in the hollow channel, and the mandrel can move along the axial direction of a first end part of the mandrel pointing to a second end part of the mandrel under the electromagnetic action generated by the electrified coil; the spindle is provided with a first permanent magnet assembly, the magnetic field setting direction of the first permanent magnet assembly is consistent with the direction of an electromagnetic field generated after the coil is electrified so as to increase the thrust force applied when the spindle moves, a second permanent magnet assembly is arranged at a position close to the first permanent magnet assembly, a repulsive force is formed between the second permanent magnet assembly and the first permanent magnet assembly, and the direction of the repulsive force is the direction in which the second end of the spindle points to the first end of the spindle so as to promote the spindle to automatically reset after the coil is powered off. The utility model discloses a solenoid actuator can increase dabber thrust and translation rate, but the dabber automatic re-setting does not need additionally to increase the voltage and the electric current of coil work, and is energy-concerving and environment-protective.

Description

Solenoid actuator

Technical Field

The present invention relates to the field of electrical components, and more particularly, to a solenoid actuator.

Background

The solenoid actuator is an electric component including a coil and a movable core, and the core is driven to move in a magnetic field direction by electromagnetic force generated by energization of the coil. Since the spindle that has moved to its position cannot be automatically reset after the coil is de-energized, the prior art solenoid actuators typically have a return spring attached to the spindle. When the coil is electrified, the electromagnetic force drives the mandrel to move, and meanwhile, the mandrel compresses the spring, so that the spring stores elastic potential energy; when the coil is powered off, the spring extends to release elastic potential energy and drive the mandrel to reset together. The thrust of the movement of the mandrel is generally related to the magnitude of the energizing current of the coil and the number of winding turns, the larger the energizing current of the coil is, the more the number of winding turns is, the stronger the magnetic field generated by the coil is, the larger the electromagnetic force is, and the larger the thrust on the mandrel is.

Although the existing solenoid actuator can realize the moving and resetting effects of the spindle, the following problems still exist: because the electromagnetic force generated by electrifying the coil not only pushes the mandrel to move, but also overcomes the resistance of the spring to the movement of the mandrel, so that the spring stores elastic potential energy, the thrust borne by the mandrel is greatly reduced, namely the fixed strength of the mandrel is weakened, and the stability and the reliability of the working state of the solenoid actuator are influenced; by increasing the current or the number of winding turns of the coil, the thrust and moving speed of the mandrel can be increased, but not only the electric energy is wasted, but also the volumes of the coil and the solenoid actuator are increased, which is not beneficial to the optimization of the overall performance of the product.

SUMMERY OF THE UTILITY MODEL

The utility model provides a solenoid actuator through setting up permanent magnet subassembly, can enough make dabber automatic re-setting, has increased the thrust of dabber simultaneously. The specific technical scheme is as follows:

a solenoid actuator comprises a shell, wherein a coil is arranged in the shell, a hollow channel is formed in the center of the coil, a mandrel is movably arranged in the hollow channel, and the mandrel can move along the axial direction of a first end part of the mandrel pointing to a second end part of the mandrel under the electromagnetic action generated by the electrified coil; the spindle is provided with a first permanent magnet assembly, the magnetic field setting direction of the first permanent magnet assembly is consistent with the direction of an electromagnetic field generated after the coil is electrified so as to increase the thrust force applied when the spindle moves, a second permanent magnet assembly is arranged at a position close to the first permanent magnet assembly, a repulsive force is formed between the second permanent magnet assembly and the first permanent magnet assembly, and the direction of the repulsive force is the direction in which the second end of the spindle points to the first end of the spindle so as to promote the spindle to automatically reset after the coil is powered off.

Further, the magnetic field setting direction of the second permanent magnet assembly is consistent with the direction of the electromagnetic field generated after the coil is electrified.

Furthermore, the first permanent magnet assembly and the second permanent magnet assembly are arranged close to the coil, so that the magnetic field of the first permanent magnet assembly and the magnetic field of the second permanent magnet assembly are superposed with the electromagnetic field generated after the coil is electrified.

Further, in the axial direction of the mandrel, the distance from the first permanent magnet assembly to the second end of the mandrel is greater than the distance from the second permanent magnet assembly to the second end of the mandrel, so that the direction of the repulsive force generated by the second permanent magnet assembly to the first permanent magnet assembly is the direction pointing to the first end of the mandrel along the second end of the mandrel.

Further, the magnetic force of the first permanent magnet assembly is greater than the magnetic force of the second permanent magnet assembly.

Further, the thickness of the first permanent magnet assembly is greater than the thickness of the second permanent magnet assembly.

Further, the coil includes first end and second end, and the first end of coil is close to the first end setting of dabber, and the second end of coil is close to the second end setting of dabber, and first permanent magnetism subassembly is fixed to be set up on the first end of dabber, and the second permanent magnetism subassembly is close to the first end setting of coil.

Further, the second permanent magnet assembly is a hollow permanent magnet, the hollow permanent magnet is fixedly arranged on the position, close to the first end portion of the mandrel, of the shell, and the hollow permanent magnet is arranged outside the mandrel and the first permanent magnet assembly in a surrounding mode.

Further, first permanent magnet subassembly includes two at least permanent magnets, and two at least permanent magnets overlap each other along the axial direction of dabber and set up.

Further, the second permanent magnet assembly comprises at least two permanent magnets, and the at least two permanent magnets are arranged in a rotational symmetry mode by taking the axis of the mandrel as a central line.

Furthermore, the first end part of the mandrel extends to the coil and the outer part of the shell, so that the first permanent magnet assembly is positioned outside the shell; the second permanent magnet assembly is attached to the end face, close to the first end portion of the mandrel, of the shell and located outside the shell.

The utility model discloses a solenoid actuator has following advantage:

1. when the coil is electrified, the intensity of the electromagnetic field generated around the mandrel is increased, so that the thrust of the mandrel is increased, the moving speed is higher, and the working state of the solenoid actuator is more stable and reliable;

2. when the coil is powered off, the mandrel can be automatically reset, and the thrust and the speed of the mandrel during moving are not influenced by the reset function;

3. under the prerequisite of realizing the dabber effect that resets and improving dabber thrust and translation rate, need not additionally to increase the operating voltage and the operating current of coil, energy-concerving and environment-protective.

Drawings

Fig. 1 is a cross-sectional view of a solenoid actuator according to the present invention in a non-energized state.

Fig. 2 is a schematic view of the working principle of the first permanent magnet assembly and the second permanent magnet assembly in the present invention.

Fig. 3 is a cross-sectional view of the solenoid actuator of the present invention in an energized state.

Fig. 4 is a bottom view of a first embodiment of a solenoid actuator according to the present invention.

Fig. 5 is a bottom view of a second embodiment of the solenoid actuator according to the present invention.

Fig. 6 is a bottom view of a third embodiment of a solenoid actuator according to the present invention.

Detailed Description

For a better understanding of the objects, structure and function of the invention, the solenoid actuator of the present invention will be described in further detail with reference to the accompanying drawings.

The utility model discloses a solenoid actuator includes the casing, is provided with the guide holder on the casing, and a holding chamber is enclosed into jointly to guide holder and casing, is provided with toroidal coil in the holding chamber. A hollow channel is formed in the central part of the annular coil, a columnar mandrel is movably arranged in the hollow channel, the first end part of the mandrel is far away from the guide seat, and the second end part of the mandrel is movably embedded in the guide seat; the coil can generate an electromagnetic field when being electrified, and the mandrel can move along the direction that the first end part of the mandrel points to the second end part of the mandrel in the axial direction of the mandrel under the action of the electromagnetism; the guide holder can play the guide effect to the moving direction of dabber, and the magnetic force that produces after guide holder and shell can be with the coil circular telegram simultaneously seals in the holding cavity.

The mandrel is provided with a first permanent magnet assembly, a second permanent magnet assembly is further arranged at a position close to the first permanent magnet assembly, and the second permanent magnet assembly is fixed relative to the coil. Repulsive force which is mutually repulsive is formed between the magnetic force generated by the first permanent magnet assembly and the magnetic force generated by the second permanent magnet assembly, the repulsive force can generate a thrust force on the mandrel, and the direction of the thrust force is the direction in which the second end of the mandrel points to the first end of the mandrel. When the coil is not electrified, the electromagnetic force generated by the coil disappears, and the mandrel which is moved at the moment can be reset under the action of the thrust formed by the repulsive force.

Preferably, the magnetic field direction of first permanent magnetism subassembly is unanimous with the electromagnetic field direction that the coil produced after the circular telegram, and first permanent magnetism subassembly is close to the coil setting, and the magnetic field of first permanent magnetism subassembly can superpose each other with the electromagnetic field that the coil produced after the circular telegram, promotes the intensity of the magnetic field effect that the dabber received, and then makes thrust increase, the translation rate that the dabber received increase.

Preferably, the magnetic field direction of second permanent magnetism subassembly is unanimous with the electromagnetic field direction that the coil produced after the circular telegram, and the setting of second permanent magnetism subassembly near coil and first permanent magnetism subassembly, and the magnetic field of second permanent magnetism subassembly can superpose each other with the electromagnetic field that the coil produced after the circular telegram and the magnetic field of first permanent magnet, further promotes the intensity of the magnetic field effect that the dabber received, increases the thrust and the translation rate of dabber.

Specifically, as shown in fig. 1, the solenoid actuator of the present invention includes a cylindrical housing 1, a housing chamber is formed inside the housing 1, a ring coil 2 is fixedly disposed in the housing chamber and is attached to the inner wall of the housing 1, and a core shaft 3 is a slender rod-shaped structure and is embedded in a hollow channel at the center of the coil 2. The mandrel 3 comprises a first end and a second end, the coil 2 comprises a first end and a second end, the first end of the coil 2 is arranged close to the first end of the mandrel 3, and the second end of the coil 2 is arranged close to the second end of the mandrel 3. When the coil 2 is energized, the electromagnetic force generated by the coil 2 can push the mandrel 3 to move in the hollow channel, and the moving direction is a direction along the first end of the mandrel 3 and points to the second end of the mandrel 3.

Further, a guide seat 4 is arranged at a position of the shell 1 close to the second end of the mandrel 3, and the guide seat 4 is fixedly connected with the shell 1. The middle part of guide holder 4 is provided with annular boss, and the boss extends the setting towards 3 first end place directions of dabber. The center department of annular boss is formed with hollow guide way, and the guide way has the guide effect, and the second end of dabber 3 inlays establishes in the guide way, can make whole dabber 3 slide along the guide way. Be provided with first inclined plane on the guide way, first inclined plane is located the guide way and is close to the terminal surface of 3 first tip of dabber, and is corresponding, and the middle part position department of dabber 3 is formed with the second inclined plane, and when dabber 3 slided along the guide way, mutual backstop can take place on first inclined plane and second inclined plane, and then the displacement of restriction dabber 3, makes the extension length of 3 second tip of dabber controllable. Adopt the mode that first inclined plane and second inclined plane mutually supported to form backstop structure, can cushion the impact force between dabber 3 and the guide holder 4 to improve the guide effect of guide holder 4 to dabber 3 moving direction.

Of course, the first inclined plane matched with structure of dabber 3 and guide holder 4 also can be a round arc line structure, or set up a plurality of tiny protruding structures on the second inclined plane to on the basis that improves buffering effect and guide effect, reduce the area of contact on dabber 3 and first inclined plane, this kind of mode of setting more does benefit to dabber 3 and guide holder 4 and breaks away from each other, in order to realize automatic re-setting.

Further, a first end of the mandrel 3 extends out of the first end of the coil 2 and the outside of the housing 1, a first permanent magnet assembly 5 is fixedly arranged on the first end of the mandrel 3, and the first permanent magnet assembly 5 is located outside the housing 1; be provided with second permanent magnetism subassembly 6 on the terminal surface that casing 1 is close to dabber 3 first end, second permanent magnetism subassembly 6 laminating is fixed on the surface of casing 1 terminal surface to make second permanent magnetism subassembly 6 be located the casing 1 outside, and be close to the first end of coil 2 and the position setting of first permanent magnetism subassembly 5.

Further, as shown in fig. 2, a repulsive force is formed between the magnetic force generated by the first permanent magnet assembly 5 and the magnetic force generated by the second permanent magnet assembly 6, and the repulsive force can be converted into a thrust force to the mandrel 3, so that the mandrel 3 is driven to move in the thrust direction. In the axial direction of the mandrel 3, the distance from the first permanent magnet assembly 5 to the second end of the mandrel 3 is greater than the distance from the second permanent magnet assembly 6 to the second end of the mandrel 3, and this arrangement can ensure that, when the coil is not energized, the direction of the repulsion force generated by the second permanent magnet assembly 6 on the first permanent magnet assembly 5 is the direction pointing to the first end of the mandrel 3 along the second end of the mandrel 3, that is, the direction of the thrust force formed by the repulsion force is the direction pointing to the first end of the mandrel 3 along the second end of the mandrel 3. After the coil 2 is electrified, the intensity of the electromagnetic force generated near the mandrel 3 is greater than the intensity of the repulsive force formed between the first permanent magnet assembly 5 and the second permanent magnet assembly 6, so when the coil 2 is electrified, the mandrel 3 can move along the direction of the first end part pointing to the second end part, and when the coil 2 is deenergized, the mandrel 3 can automatically reset under the pushing of the repulsive force.

Further, as shown in fig. 3, the direction of the magnetic field of the first permanent magnet assembly 5 is consistent with the direction of the electromagnetic field generated after the coil 2 is electrified, and since the first permanent magnet assembly 5 is disposed close to the coil 2, the magnetic field of the first permanent magnet assembly 5 and the electromagnetic field generated after the coil 2 is electrified can be mutually superposed. The direction of the magnetic field of the second permanent magnet assembly 6 is also consistent with the direction of the electromagnetic field generated after the coil 2 is electrified, and the second permanent magnet assembly is arranged close to the coil 2 and the first permanent magnet assembly 5, so that the magnetic field of the second permanent magnet assembly 6 can be mutually superposed with the electromagnetic fields generated by the first permanent magnet assembly 5 and the electrified coil 2. Compared with the acting force only subjected to the electromagnetic field of the coil 2, after the magnetic fields of the first permanent magnet assembly 5 and the second permanent magnet assembly 6 are superposed with the electromagnetic field of the coil 2, the acting strength of the magnetic field applied to the mandrel 3 is obviously improved, so that the thrust applied to the mandrel 3 is increased, the moving speed is increased, the holding force applied to the mandrel 3 after moving is increased, and the working state of the solenoid actuator is more stable and reliable.

Preferably, the magnetic force of the first permanent magnet assembly 5 is greater than the magnetic force of the second permanent magnet assembly 6. In this arrangement, the electromagnetic field of the coil 2 is enhanced by the first permanent magnet assembly 5 more than the repulsion between the second permanent magnet assembly 6 and the first permanent magnet assembly 5. That is, when the coil 2 is energized, the thrust force generated by the magnetic field of the first permanent magnet assembly 5 on the mandrel 3 is greater than the repulsive force between the second permanent magnet assembly 6 and the first permanent magnet assembly 5. That is to say, although a part of the electromagnetic field generated by the energized coil 2 needs to be used for overcoming the repulsive force between the second permanent magnet assembly 6 and the first permanent magnet assembly 5, the thrust action of the first permanent magnet assembly 5 on the mandrel 3 is stronger when the coil 2 is energized, so that the mandrel 3 cannot be decelerated or the moving thrust is reduced due to the repulsive force between the first permanent magnet assembly 5 and the second permanent magnet assembly 6, and the effect of increasing the thrust and the moving speed of the mandrel 3 can be achieved under the condition that the current and the voltage are unchanged.

Preferably, the thickness of the first permanent magnet assembly 5 is greater than that of the second permanent magnet assembly 6, i.e. the distance from the surface of the N-pole end of the first permanent magnet assembly 5 to the surface of the S-pole end is greater than that of the second permanent magnet assembly 6. As shown in fig. 3, when the mandrel 3 is in the extended state under the action of the electromagnetic field, the first permanent magnet assembly 5 will move towards the inner direction of the housing 1; when moving to the extreme position, one end face of the first permanent magnet assembly 5 facing the second end of the spindle 3 will exceed the end face of the second permanent magnet assembly 6 facing the second end of the spindle 3, and because the thickness of the first permanent magnet assembly 5 is larger, the end face of the first permanent magnet assembly 5 facing away from the second end of the spindle 3 will also exceed the end face of the second permanent magnet assembly 6 facing away from the second end of the spindle 3.

By adopting the arrangement mode, on one hand, the first permanent magnet assembly 5 and the second permanent magnet assembly 6 can be ensured to always keep a mutually exclusive state under the condition of power failure of the coil, so that the mandrel 3 can be automatically reset; on the other hand, when the coil is electrified, the first permanent magnet assembly 5 and the second permanent magnet assembly 6 are influenced by the electromagnetic field from the coil 2, the first permanent magnet assembly 5 moves towards the second permanent magnet assembly 6 along with the mandrel 3, when the magnetic line of force of the first permanent magnet assembly 5 crosses the magnetic field center line of the second permanent magnet assembly 6, the repulsive force between the first permanent magnet assembly 5 and the second permanent magnet assembly 6 is converted into attractive force, the mandrel 3 is attracted to extend out to move, and the thrust of the mandrel 3 is further enhanced. When the coil 2 is powered off again, the electromagnetic field generated by the coil disappears, and the first permanent magnet assembly 5 and the second permanent magnet assembly 6 are restored to a state of generating repulsive force with each other, so that the mandrel 3 is automatically reset.

Preferably, as shown in fig. 4, the second permanent magnet assembly 6 is a hollow permanent magnet, a hollow structure is formed in a central portion of the hollow permanent magnet, the hollow permanent magnet is fixedly disposed on the casing 1 near the first end of the spindle 3, and the hollow permanent magnet is disposed around the exterior of the spindle 3 and the first permanent magnet assembly 5, that is, the spindle 3 is located in the hollow structure in the central portion of the hollow permanent magnet. By adopting the arrangement mode, the action effect between the first permanent magnet component 5 and the second permanent magnet component 6 can be promoted to the maximum extent, and the stability of the action effect is improved. The hollow permanent magnet is preferably a circular ring permanent magnet to match the shape of the bottom end face of the housing 1, and may be elliptical ring, rectangular, or other shapes.

The second permanent magnet assembly 6 is preferably formed by one integrally formed hollow permanent magnet, or the second permanent magnet assembly 6 may be formed by two or more hollow permanent magnets which are overlapped with each other along the axial direction of the mandrel. Of course, the second permanent magnet assembly 6 may also be composed of at least two permanent magnets, and the at least two permanent magnets are rotationally symmetrically arranged with the axis of the mandrel 3 as the center line to interact with the first permanent magnet assembly 5, so as to achieve the effect of automatic resetting of the mandrel 3. For example, as shown in fig. 5 and 6, the second permanent magnet assembly 6 includes 4 cylindrical permanent magnets, and the 4 permanent magnets are rotationally symmetrically arranged with the axis of the mandrel 3 as the center line; or, the second permanent magnet assembly 6 includes 2 bar or curved permanent magnets, and 2 permanent magnets are arranged in a rotational symmetry manner with the axis of the mandrel 3 as the center line. The magnetic force of the second permanent magnet assembly 6 can be adjusted by increasing or decreasing the number of permanent magnets stacked in the second permanent magnet assembly 6, or by adjusting the number of permanent magnets disposed around the spindle.

The first permanent magnet assembly 5 is preferably formed by an integrally formed cylindrical permanent magnet, preferably having the same outer diameter as the mandrel, fixedly arranged at the first end of the mandrel. Alternatively, the first permanent magnet assembly 5 may be composed of two or more permanent magnets, and the two or more permanent magnets are arranged to overlap each other along the axial direction of the mandrel. This arrangement allows the magnitude of the magnetic force of the first permanent magnet assembly 5 to be adjusted by increasing or decreasing the number of permanent magnets that overlap.

Further, in addition to the preferred arrangement described above, the first and second

permanent magnet assemblies

5, 6 may also be arranged in other ways, such as: the second permanent magnet assembly 6 can also be arranged in the middle of the shell 1 or at a position of the shell 1 close to the second end of the mandrel 3, as long as a repulsive force for resetting the mandrel 3 can be generated between the second permanent magnet assembly 6 and the first permanent magnet assembly 5; alternatively, the second permanent magnet assembly 6 may also be disposed inside the housing 1, such as being fixedly connected to the inner wall of the end portion of the housing 1, or fixedly connected to the inner wall of the middle portion of the housing 1; alternatively, the first permanent magnet assembly 5 may be disposed at a middle position of the mandrel 3, and correspondingly, the fixing position of the second permanent magnet assembly 6 is closer to the second end of the mandrel 3 than the position of the first permanent magnet assembly 5, so as to ensure that the direction of the thrust generated by the repulsive force on the mandrel 3 can cause the mandrel 3 to automatically reset.

The operation of the solenoid actuator of the present invention will be briefly described with reference to fig. 2 and 3. As shown in fig. 2, when the coil 2 is not energized, the mandrel 3 remains stable in the retracted position under the effect of the repulsion forces generated between the first and second

permanent magnet assemblies

5, 6; when the coil 2 is electrified, as shown in fig. 3, an electromagnetic field is generated around the coil 2, and the magnetic field of the first permanent magnet assembly 5 and the electromagnetic field of the coil 2 are mutually overlapped, so that the mandrel 3 is accelerated to move and extend out, and the thrust of the mandrel 3 is improved; when the coil 2 is powered off again, the electromagnetic field disappears, the superposition effect of the magnetic field of the first permanent magnet assembly 5 and the electromagnetic field also disappears, and the mandrel 3 can automatically reset under the action of the repulsive force between the first permanent magnet assembly 5 and the second permanent magnet assembly 6.

The utility model discloses a solenoid actuator has following advantage:

The present invention has been further described with reference to specific embodiments, but it should be understood that the specific description herein should not be construed as limiting the spirit and scope of the present invention, and that various modifications to the above-described embodiments, which would occur to persons skilled in the art after reading this specification, are within the scope of the present invention.

Claims

1. A solenoid actuator is characterized by comprising a shell, wherein a coil is arranged in the shell, a hollow channel is formed in the center of the coil, a mandrel is movably arranged in the hollow channel, and the mandrel can move along the axial direction of a first end part of the mandrel pointing to a second end part of the mandrel under the electromagnetic action generated by the electrified coil; the spindle is provided with a first permanent magnet assembly, the magnetic field setting direction of the first permanent magnet assembly is consistent with the direction of an electromagnetic field generated after the coil is electrified so as to increase the thrust force applied when the spindle moves, a second permanent magnet assembly is arranged at a position close to the first permanent magnet assembly, a repulsive force is formed between the second permanent magnet assembly and the first permanent magnet assembly, and the direction of the repulsive force is the direction in which the second end of the spindle points to the first end of the spindle so as to promote the spindle to automatically reset after the coil is powered off.

2. The solenoid actuator of claim 1 wherein the magnetic field of the second permanent magnet assembly is oriented in a direction that is consistent with the direction of the electromagnetic field generated by the coil when energized.

3. The solenoid actuator of claim 2, wherein the first permanent magnet assembly and the second permanent magnet assembly are disposed proximate the coil such that a magnetic field of the first permanent magnet assembly and a magnetic field of the second permanent magnet assembly overlap an electromagnetic field generated by energizing the coil.

4. The solenoid actuator of claim 1 wherein the distance in the direction of the axis of the spindle between the first permanent magnet assembly and the second end of the spindle is greater than the distance between the second permanent magnet assembly and the second end of the spindle such that the direction of the repulsion of the first permanent magnet assembly by the second permanent magnet assembly is in a direction pointing along the second end of the spindle toward the first end of the spindle.

5. The solenoid actuator of claim 1, wherein the magnetic force of the first permanent magnet assembly is greater than the magnetic force of the second permanent magnet assembly.

6. The solenoid actuator of claim 1, wherein the thickness of the first permanent magnet assembly is greater than the thickness of the second permanent magnet assembly.

7. The solenoid actuator of any one of claims 1 to 6 wherein the coil includes a first end and a second end, the first end of the coil being disposed proximate the first end of the mandrel and the second end of the coil being disposed proximate the second end of the mandrel, the first permanent magnet assembly being fixedly disposed on the first end of the mandrel and the second permanent magnet assembly being disposed proximate the first end of the coil.

8. The solenoid actuator of claim 7 wherein the second permanent magnet assembly is a hollow permanent magnet fixedly disposed in the housing adjacent the first end of the spindle, the hollow permanent magnet disposed circumferentially about the spindle and the exterior of the first permanent magnet assembly.

9. The solenoid actuator of claim 7, wherein the second permanent magnet assembly comprises at least two permanent magnets, the at least two permanent magnets being rotationally symmetric about the axis of the spindle.

10. The solenoid actuator of claim 8 or 9 wherein the first permanent magnet assembly comprises at least two permanent magnets arranged one above the other in the axial direction of the spindle.

11. The solenoid actuator of claim 8 or 9, wherein the first end of the core shaft extends to an exterior location of the coil and the housing such that the first permanent magnet assembly is located outside the housing; the second permanent magnet assembly is attached to the end face, close to the first end portion of the mandrel, of the shell and located outside the shell.