JPH0611181B2 - Linear actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an apparatus for performing linear position control, and particularly for minute position control.

[Conventional technology]

Conventionally, there have been mainly two methods as means for performing linear position control.

The first method is to detect the position of the controlled object itself by an appropriate detecting means and feed it back.

In the second method, a positioning motor or the like is used to convert the rotary motion into a linear motion.

[Problems to be solved by the invention]

The problems with the first method are as follows.
That is, (1) the detection means (position sensor) must be provided directly or in close proximity to the controlled object, and this has the drawback of impairing the degree of freedom in device design.

(2) Further, there is a problem in that the detection means itself cannot be attached or the detection means must be attached at an inappropriate position, for example, when the object to be controlled is located at an inappropriate place.

The problem with the second method is that it requires a linear conversion mechanism for converting rotational motion into linear motion. This also impairs the degree of freedom in design, and the linear conversion mechanism itself has a high level of technology.

The present invention has been made in view of these points, and realizes a small-sized and inexpensive linear actuator.

[Means for solving problems]

Therefore, the linear actuator of the present invention detects the leakage flux from the fixed portion having the magnetic flux generation means, the coil arranged so that the main magnetic flux from the magnetic flux generation means penetrates, and the leakage magnetic flux from the magnetic flux generation means. A movable part having a magnetic sensing element for outputting a signal according to the strength of the moving part, power supply means for supplying electric power based on a moving part up / down signal to the coil, and output of the magnetic sensing element to the power supply means. As a configuration having feedback means for feeding back, the strength of the leakage flux of the magnetic flux generating means of the fixed part sensed by the magnetic sensing element when the movable part is moved up and down by the power supply means is used as a position control element. There is.

[Action]

The coil and the magnetic sensing element are arranged at different positions so that the main magnetic flux of the magnetic flux generated from the magnetic generation means acts on the coil of the movable portion and the leakage magnetic flux acts on the magnetic sensing element.

Since the intensity of the leakage magnetic flux becomes smaller according to the distance from the magnetism generating means, the position of the movable portion can be detected by the output of the magnetic sensing element.

〔Example〕

FIG. 1 is a structural explanatory view showing an embodiment of the present invention and shows a cross section of a cylindrically formed member.

In the figure, 10 is a yoke, 11 is a permanent magnet (hereinafter, simply referred to as magnet) as a magnetic flux generating means, 12 is an iron core, 1
3 is a coil, 14 is a coil holder, 15 is a guide shaft, 1
6 is a bearing, 17 is a fixing screw, and 18 is a Hall element as a position detector.

A magnetic circuit is formed by the yoke 10, the magnet 11 and the iron core 12. The flow of magnetic flux originates from the N pole of the magnet 11, passes through the iron core 12 and the yoke 10, and enters the S pole of the magnet 11.
This magnetic circuit serves as the main path of the magnetic flux, and contains most of the magnetic flux from the magnet 11 (main magnetic flux).

The coil 13, the coil holder 14, and the guide shaft 15 serve as a movable portion, and the coil 13 of the movable portion is arranged between the yoke 10 and the iron core 12 that form the above-described magnetic circuit.
At this time, by supplying an electric current to the coil 13, the movable part is displaced up and down and operates as an actuator.

A Hall element 18 is embedded in the movable portion as a position detector that detects the position of the movable portion.

The movable part is displaced in accordance with the current supplied to the coil 13, and thus the hall element 18 is displaced.

On the other hand, not only the magnetic flux just for displacing the movable part from the magnetic circuit, but also the leakage magnetic flux is always present. A part of this leakage magnetic flux is emitted from the iron core 12 and penetrates the Hall element 18. The magnetic flux density due to this leakage magnetic flux decreases with distance.

Therefore, by displacing the movable portion, that is, the Hall element 18, the output shown in FIG. 2 can be obtained and the servo loop shown in FIG. 3 can be configured. In FIG. 3, 2 is an error amplifier, 3 is a power amplifier, and 4 is a feedback circuit.

By using the servo loop as shown in FIG. 3, position control as a linear actuator can be performed very easily.

For example, it can be applied in a very wide range such as a pen driving unit of a recording device and a valve control for controlling a flow rate.

Further, since the position detector is embedded in the actuator itself, it can be manufactured in a small size and at a low cost.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a linear actuator that is simple in structure, small in size, and inexpensive.

[Brief description of drawings]

FIG. 1, FIG. 2 and FIG. 3 are configuration explanatory views showing an embodiment of the present invention. 10 ... York, 11 ... Magnet, 12 ... Iron core, 13 ...
... Coil, 14 ... Coil holder, 18 ... Hall element

Claims (1)

[Claims] 1. A fixed portion having a permanent magnet as a magnetic flux generating means, a coil arranged so that a main magnetic flux generated by the magnetic flux generating means of the fixed portion penetrates, and a leakage generated by the magnetic flux generating means. A movable part having a magnetic sensing element that senses a magnetic flux and outputs a signal corresponding to the strength of the leakage magnetic flux; power supply means for supplying electric power based on a movable part up / down signal to a coil of the movable part; Feedback means for feeding back the output of the magnetic sensing element to the power supply means, and the magnetic flux generating means of the fixed part sensed by the magnetic sensing element when the movable part is moved up and down by the power supply means. A linear actuator characterized in that the intensity of leakage magnetic flux is used as position information.