JPH058649Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) The present invention relates to a linear drive device used for adjusting the opening of a valve, for example.

(Prior Art) A conventional linear drive device of this type has a configuration in which an excitation coil is slidably provided with an iron core serving as a plunger. Then, the plunger is driven by exciting the exciting coil.

However, when the iron core moves, the path of the magnetic flux changes, and this change causes a change in the force acting on the plunger, that is, the thrust. Especially in the case of a simple structure, if the core moves more than a few millimeters, the thrust will change significantly.

In order to prevent the thrust from changing even if the iron core is moved in this way, two iron cores, which are plungers, are arranged in series, and the positions where the thrust of each plunger reaches its maximum value relative to the movement of the iron core are shifted. A configuration is known in which the thrust is averaged.

However, providing two plungers complicates the structure, and depending on how the position of the iron core is shifted, valleys or unevenness may occur in the thrust force. Furthermore, if the number of iron cores serving as plungers is increased in order to increase the moving distance, the structure of the device becomes even more complex.

In addition, as another configuration in which the thrust force does not change even when the iron core moves, a gentle taper is provided in the iron core or the magnetic path that attracts the iron core in the direction that attracts the iron core, which is a plunger, so that the amount of change in magnetic flux with respect to movement There are known configurations that reduce the

However, the smoother the taper, the greater the wasted component of force in the direction perpendicular to the thrust, and this component of force becomes a force that eccentrically attracts the iron core, which is the plunger, to the side of the excitation coil. , friction increases, and as a result, the desired thrust may not be obtained or the hysteresis of movement will increase.

(Problems to be Solved by the Invention) In the conventional configuration in which two or more iron cores are provided, the structure becomes complicated and the thrust may become unbalanced.

In addition, in a configuration in which the iron core or the magnetic path that attracts the iron core has a gentle taper, unnecessary force in the direction perpendicular to the thrust increases, and this force causes the iron core, which is the plunger, to exert a strong force on the side of the excitation coil. This creates an eccentric suction force, which increases friction, resulting in problems such as not being able to obtain as much thrust as expected and increasing hysteresis in movement.

The present invention was devised in view of the above-mentioned problems, and it is an object of the present invention to provide a linear drive device that has a simple structure and can obtain smooth and powerful thrust.

[Structure of the idea]

(Means for Solving the Problems) A linear drive device of the present invention includes an iron core and an excitation coil into which the iron core is slidably inserted and has a magnetic path, the iron core and the excitation coil facing each other. As the length of the magnetic path decreases, the opposing area per unit of the iron core and the magnetic path decreases.

(Function) In this invention, as the length of the iron core facing the excitation coil becomes shorter, the facing area per unit length between the iron core and the magnetic path becomes smaller, magnetic resistance increases, and is concentrated in a small area. The iron core slides with the applied force. Conversely,
As the opposing length of the iron core and the magnetic path increases, the opposing area per unit area of the iron core and the magnetic path increases, reducing magnetic resistance, and the force is distributed over a wide area, causing the core to slide. do. In this way, smoothed thrust is obtained even if the iron core moves.

(Embodiment) Hereinafter, an embodiment of the linear drive device of the present invention will be described with reference to the drawings.

In Fig. 1, 1 is a magnetic path section that also serves as a frame;
This magnetic path section 1 holds the excitation coil 2 so as to wrap it around it, and a cylindrical recess 3 with one end closed is provided in the center of the magnetic path section 1 in the axial direction. has a gap 4 that does not completely cover the excitation coil 2. As shown in FIGS. 2 and 3, this gap 4 has a notch on the stator side diagonally with respect to the sliding direction, and has a triangular protrusion projecting downward as a magnetic path. A so-called skewed magnetic path body 5 is attached, and the lower part forms a triangular gap 4 that becomes wider as it goes downward.

Further, a plunger 6 as an iron core is slidably provided in the recess 3, a shaft 7 is provided on both sides of the plunger 6, and one end of this shaft 7 is connected to the magnetic path section 1.
It is slidably and rotatably inserted into the bearing 8 of.

Next, the operation of the above embodiment will be explained.

First, when the upper end of the plunger 6 is at the position _P1 , the magnetic flux is concentrated in the _a1 and _a2 parts of the magnetic path body 5, and the attractive force is generated from the _a1 and _a2 parts. After that, as the plunger 6 is attracted and the tip of the plunger 6 moves toward position P ₂ , the magnetic flux spreads to triangles a ₁ , b ₁ , c ₁ and triangles a ₂ , b ₂ , and c ₂ of the magnetic path body 5. ,
Magnetic resistance decreases. Furthermore, when the plunger 6 is attracted and the tip of the plunger 6 reaches the position _P3 , the magnetic flux is transferred to the triangle _a1de and the triangle _a2ed of the magnetic path body 5.
That is, it spreads over almost the entire magnetic path body 5, and the magnetic resistance becomes extremely small. Further, when the tip of the plunger 6 rises above the position _P3 , the thrust force decreases.

That is, magnetic resistance Rm is determined by magnetic permeability μ, distance l,
If the area is S, it is expressed as Rm=l/μS, and the larger the area, the smaller the magnetic resistance.

While moving from position P ₁ to position P ₃ in Figure 1, the magnetic flux changes smoothly along the skewed magnetic path body 5 and the magnetic resistance decreases, as shown in Figure 4. As shown, the thrust exhibits smooth characteristics with respect to the position of the plunger 6.

Further, the magnetic path body 5 is not limited to providing a so-called triangular skew, but a triangular skew projecting above the plunger 6 may be provided.

Furthermore, the number of triangular protrusions is not limited to two, but one.
It may be one or a plurality of three or more.

In addition, by changing the length, shape, etc. of the protrusion, the relationship between the moving position of the core and the thrust can be arbitrarily set, which allows easy design and manufacturing.

[Effect of idea]

According to the present invention, as the opposing length of the iron core and the exciting coil becomes shorter, the opposing area per unit of the iron core and the magnetic path becomes narrower, so that the change in thrust is smooth, and The structure is simple because multiple iron cores are not used.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view along the line shown in Fig. 3 of a linear drive device according to an embodiment of the present invention, Fig. 2 is a developed view of the same magnetic path, Fig. 3 is a plan view of the same, and Fig. 4 is an iron core. This is a graph showing the relationship between thrust and force. 2...excitation coil, 5...magnetic path body as a magnetic path, 6...plunger as an iron core.

Claims (1)

[Claims for Utility Model Registration] An iron core, an excitation coil that is slidably inserted into the iron core and has a magnetic path, and as the length of the opposing length of the iron core and the excitation coil becomes shorter, . A linear drive device characterized in that a unit facing area of the iron core and the magnetic path is narrow.