JPH0441332Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotation sensor using Wiegand wire.

Wiegand wire is a magnetic wire named after its inventor.
It is known from the publication No. 15797.

That is, such magnetic wire comprises a drawn wire of a suitable ferromagnetic material having a generally circular cross-section, as shown at 10 in FIG. Preferably, the wire has a perfect circular cross section or a cross section close to a perfect circle,
It is processed to form a magnetic wire core 14 with relatively low retentivity and coercivity and a magnetic wire shell 16 with relatively high retentivity and coercivity. Core 14 has an easy axis parallel to the axis of the wire and is magnetically anisotropic. Shell 16 also has an easy axis parallel to the axis of the wire, is magnetically anisotropic, and is magnetized to form N and S at its ends.
The shell 16 has sufficiently greater remanence and coercivity than the core 14, so that the shell 16 can be magnetized by magnetizing the core 14 in an axial direction opposite to the axis of magnetization of the shell 16. It is coupled to the core 14. Therefore,
The core 14 is connected to the shell 16 by the magnetic flux lines shown in FIG.
A magnetic domain intermediate region 18 is formed between the core and shell between lines of magnetic flux that extend in opposite directions within the core and shell to form a magnetic return path or shunt toward the core and shell.

Shell 16 can be magnetized in either axial direction. In the absence of an external magnetic field, the relatively high coercive force of the shell 16 restrains the core 14 such that the remanence of the core 14 is in the opposite direction of the remanence of the shell 16.

The direction of magnetization of the core 14 is switched by using an external magnetic field that counteracts the effect of the shell 16. For example, a sufficiently strong bar magnet can be connected to a wire 1
When placed close to the wire 10 parallel to 0 and with the magnetic poles opposite the magnetism of the wire shell 16, this bar magnet constrains the core 14 and reverses the direction of the core's residual magnetism. Switching occurs when the strength of the external magnetic field from the external bar magnet exceeds the strength of the magnetic field from the shell 16 at the core 14. The extent to which the magnetic field strength of a bar magnet must be greater than the magnetic field strength of the shell depends on the magnitude of the magnetic anisotropy of the core.

In the process of switching the remanence of the core, the contribution of the shell to the external magnetic field changes greatly in magnitude and changes rapidly over time. As a result, a suitably placed pick-up coil generates a pulse to detect (read) a reversal in the direction of the magnetic flux in the core.

When the shell constrains the core, which was previously constrained by an external magnetic field, the net change in the external magnetic field is such that the shell's magnetic field has a path through the core, so that it is vectorially subtracted from the external magnetic field. This results in a relatively large magnetic field at the pickup coil. Similarly, when an external magnetic field constrains the core that was previously constrained by the shell, the magnetic field due to the shell is completed outside the wire 10 and is therefore added vectorially to the external magnetic field, causing a relatively small amount of force in the pick-up coil. bring about a magnetic field. As a result, the direction of the magnetic flux within the pickup differs depending on the direction in which the core magnetization is switched.

[Conventional technology]

Conventionally, rotation sensors constructed using the above-mentioned magnetic wire are shown in FIGS. 6 and 7.

In FIG. 6, two magnets 20 are placed side by side at a constant interval so that their magnetic poles are opposite to each other.
A magnetic wire 22 with a pickup coil 21 wound thereon is arranged between a and 20b with its longitudinal direction aligned with the magnetic pole direction, and one magnet 20
The impeller 23 is arranged so that the blades 23a of the impeller 23 pass through the gap between the magnetic wire 22 and the magnetic wire 22 by rotation thereof. With this configuration, when the impeller 23 rotates, a pulse-like electric signal having a period inversely proportional to the rotational speed of the impeller 23 is connected to the pickup coil 21.

In FIG. 7, a plurality of rod-shaped magnets 31 are provided at equal intervals on the circumferential surface of the rotating body 30 with their longitudinal directions aligned with the rotating axis direction, and the rotating body 30
A magnetic wire 33 around which a pickup coil 32 is wound is provided adjacent to the magnet 31 so that its longitudinal direction coincides with the rotational axis direction of the rotating body 30.
is magnetized so as to alternately exhibit N and S poles in the radial direction on the rotating body 30. and rotating body 30
As it rotates, the N and S poles alternately face the magnetic wire 33, thereby inducing a pulse-like electrical signal in the pickup coil 32 with a period inversely proportional to the rotational speed of the rotating body 30. be done.

Any of the rotation sensors described above includes an impeller 23,
The same electric signal is obtained at the pickup coils 21 and 32 no matter which direction the rotating body 30 rotates.

[Problem that the invention attempts to solve]

As mentioned above, conventional rotation sensors can obtain output in both rotational directions, so for example, in a gas meter, the impeller and rotating body are rotated according to the gas flow, and the gas flow rate is measured by the electric signal generated at this time. In this case, the electric signal generated when the gas flows backward for some reason and the impeller and rotating body are reversed causes an error in the measurement of the gas flow rate.

Therefore, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a rotation sensor that outputs an electric signal only during rotation in one direction.

[Means for solving problems]

In order to achieve the above object, the rotation sensor according to the present invention has at least four magnets with alternately different magnetic poles arranged at equal intervals on the same circle concentric with the rotation axis of the rotating disk, and a shell portion and A pick-up coil is wound around a magnetic wire having a core, and at least the shell can retain residual magnetism by being placed in a magnetic field, and the retaining force of the shell is sufficiently larger than that of the core. A magnetic wire is placed parallel to the rotating disk at a distance from the surface of the magnet, and its longitudinal direction coincides with a line connecting adjacent magnets at a predetermined rotational position of the rotating disk, and in this state, one of the magnets becomes magnetic. The magnetic wire is characterized by being disposed so as to face approximately the center of the wire, with the other magnet located away from the end of the magnetic wire.

[Effect]

In the above configuration, the present invention provides that, in the process in which the magnetic wire is magnetized by an external magnetic field, the magnetization speed is different between the core and the shell at the center and ends of the magnetic wire, and the magnet is transferred from the center to the end. This was based on the experimental results that showed that as the magnet approaches the center, the magnetic reversal speed at the core increases, but when the edge approaches the center, the magnetic reversal speed slows down. Placing the magnetic wire and the rotating disk containing the magnet in such a relationship that only in rotation the magnet moves from the center to the ends of the magnetic wire, but not in other directions of rotation. This makes it possible to detect rotation in one direction.

[Example of idea]

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIGS. 1 and 2 are a plan view and a side view, respectively, showing an embodiment of the rotation sensor according to the present invention, in which the rotating disk 40 rotates counterclockwise in conjunction with mechanical movement of a gas meter or the like. . rotating disk 4
0 has four magnets 41a to 41a arranged on the same circle concentric with the center of rotation at equal intervals of 90 degrees.
41d. These magnets 41a-4
1d is magnetized so that its surface alternately exhibits different polarities. A magnetic wire 42 is placed at a certain distance from the surface of the magnets 41a to 41 on the rotating disk 40 and parallel to the disk surface. The magnetic wire 42 has a pickup coil 43 wound around its outer periphery, and extends along a line connecting a pair of adjacent magnets at a predetermined rotational position of the disk 40, and in this state, only one magnet is magnetic. It is positioned so as to face approximately the center of the wire 42.

As described above, when the rotating disk 40 rotates counterclockwise, the magnet facing the center of the magnetic wire 42 moves toward the end of the magnetic wire 42. When this magnet leaves the end of the magnetic wire 42, the next magnet of a different polarity comes to face the center of the magnetic wire 42, so that two magnets do not face the magnet at the same time.

Now, as shown in FIG. 3, the longitudinal directions of the magnetic wire 42 are +Y and -Y directions, and the directions perpendicular to these at the center 0 of the magnetic wire 42 are +X and -X directions. The part surrounded by X and +Y, -X and -Y, +X and -Y, +X and -Y is the th, th,
The second quadrant. In this state, the magnet moves from the central part 0 of the magnetic wire 42 to +Y or -
When it moves in the Y direction and comes off the end of the magnetic wire 42 and the next magnet comes to face the center part 0 of the magnetic wire, an electric signal is obtained at the pick-up coil 43.Contrary to the above case, +Y or −
When the magnet moves from the Y direction to the center 0 of the magnetic wire 42, no electrical signal is obtained at the pickup coil 43. ” Therefore, when the magnets 41a to 41c arranged on the rotating disk 40 are in the second and second quadrants, the electric signal obtained by the pickup coil 43 is the same as when the rotating disk 40 rotates clockwise. When the position is in the first quadrant, an electric signal is obtained at the pickup coil 43 when the rotating disk 40 rotates counterclockwise.

By the way, as mentioned above, when the magnets 41a to 41c arranged on the rotating disk 40 are in a predetermined quadrant, an electric signal can be obtained only when rotating in one direction, and cannot be obtained when rotating in the other direction. The reason will be explained below.

Generally, the magnetic wire 42 has hysteresis when the magnetic pole reverses, and the magnetic pole can reverse beyond this hysteresis only when the magnet moves away from the center of the magnetic wire 42 toward the ends. Therefore, when approaching the center from the edge, the hysteresis cannot be overcome.

This is because, in the process in which the magnetic wire 42 is magnetized by an external magnetic field, the magnetization speed is different between the core and the shell at the center and ends of the magnetic wire 42.
This is based on experimental results showing that when a magnet approaches an edge from the center, the magnetic reversal speed at the core increases, but when a magnet approaches the center from an edge, the magnetic reversal speed slows down. As a result, as the external magnetic field increases, reversal is more likely to occur at the core at the ends, and the reversal speed at the center is approximately the same between the shell and the core.

From the above, the signal output during rotation in one direction is such that when the magnet moves from the center of the magnetic wire to the end and comes off, the change in the magnetic field received by the core of the magnetic wire is greater, and therefore the change in the magnetic field at the core is greater. The switching of the direction of magnetization occurs at high speed and a large electrical signal is induced in the pick-up coil, whereas the electrical signal induced in the pick-up coil when the magnet moves from the end of the magnetic wire to the center is small. This is done by identifying the magnitude of this signal.

With the above-described configuration, one revolution of the rotating disk 40 provides an electrical signal consisting of pulses corresponding to the number of magnets on the disk. Therefore, by increasing the number of magnets to six as shown in FIG. 4, six pulses can be generated in response to one rotation of the disc 40.

[Effect of idea]

As explained above, according to the present invention, when the magnet moves from the center of the magnetic wire to the end and comes to a position away from the end, the next different magnetic pole will face the center of the magnetic wire. Since a signal is extracted from the electric signal to the pick-up coil only when the rotating disk rotates, where such movement of the magnet occurs, it is possible to detect rotation in one direction, and it is useful for measuring gas flow rate, for example. You will get what is suitable.

[Brief explanation of the drawing]

Figures 1 and 2 are a plan view and side view showing one embodiment of the invention, Figure 3 is an explanatory diagram for explaining the principle of the invention, and Figure 4 is a plan view showing another embodiment. , FIG. 5 is a diagram for explaining the operation of the Wiegand wire, and FIGS. 6 and 7 are perspective views showing examples of conventional rotation sensors, respectively. 40...Rotating disk, 41a-41d...Magnet, 42...Magnetic wire, 43...Pickup coil.

Claims (1)

[Scope of utility model registration request] At least four magnets with alternating magnetic poles are provided on the same circle concentric with the rotational axis on a rotating disk, and have a shell portion and a core portion, and at least the shell portion is placed in a magnetic field. The pick-up coil is wound around a magnetic wire whose shell part has a sufficiently larger retentive force than the core part, and the magnetic wire is separated from the surface of the magnet and parallel to the rotating disk. At a predetermined rotational position of the rotating disk, the longitudinal direction of the magnets coincides with a line connecting adjacent magnets, and in this state, one magnet faces approximately the center of the magnetic wire, and the other magnet faces the center of the magnetic wire. A rotation sensor characterized by being located at a position off the edge.