JPS5931879B2 - potentiometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a potentiometer using a magnetoresistive element.

In this type of potentiometer, the configuration of the magnetic circuit has a large effect on the final performance variation.

The magnetic circuit of a potentiometer is usually
Publication No. 4587 "Variable resistor using magnetoresistive element"
As shown in , it is configured as a closed magnetic path together with a bottomed cylindrical core, a rotating magnetic body, and a permanent magnet, and a magnetoresistive element is placed in a gap formed at the tip of the rotating magnetic body.
It is designed to generate output according to the rotation of the rotating magnetic body. Further, the potentiometer described above obtains a predetermined function output from the magnetoresistive element by changing the gap between the tips of the rotating magnetic body, in other words, by processing the tip of the rotating magnetic body with a predetermined function. However, it is difficult to process the tip of a rotating magnetic material so that it has a predetermined functional shape, and the effect of the functional shape cannot be obtained unless the shaft diameter is increased, and the gap has narrow parts and wide parts. The magnetic flux concentrates in a narrow area, making it impossible to obtain uniform magnetic flux density.
This is undesirable in consideration of the square-law characteristics of the magnetoresistive element. For this reason, in recent years, in order to solve these problems, potentiometers have been developed by making the gap between the tips of the rotating magnetic body constant, and semicircular. A magnetic piece with a uniform magnetic flux density is configured to rotate around a rotation axis.

However, when the semicircular magnetic piece shown by the solid line in Fig. 1 gives magnetic flux B1 to the magnetoresistive element, the magnetic flux density B acting on the magnetoresistive element has a distributed distribution as shown in Fig. 2a. Show characteristics.

This means that when the magnetic piece rotates, the magnetic flux to the magnetoresistive element changes slowly, or in other words, the magnetic flux is not easily cut. Therefore, in such a magnetic piece, the output obtained from the magnetoresistive element is as shown in FIG. 3a,
The curve becomes sinusoidal with respect to the rotation angle θ, resulting in poor linearity. For this reason, although it can be effective for equipment that requires a sinusoidal output, the inferior linearity has been an obstacle for the most basic equipment that displays the rotation angle as an electrical quantity. The present invention has been made to solve the above-mentioned drawbacks.
A detailed explanation will be given below using the accompanying drawings. FIG. 4 shows a cross-sectional view of the potentiometer.

A non-magnetic substrate 12 in which a cylindrical magnet 11 is embedded is installed at the bottom of the bottomed cylindrical magnetic case 10 . The magnet 11 may be constructed by drilling a hole in the substrate 12 and fitting into the hole, or may be insert-molded at the same time as the substrate 12 is formed. Further, a terminal pin 13 is embedded in the board 12 like a magnet, one end protrudes outside the case 10, the other end projects inside the case 10, engages with the terminal plate 14, and is connected to the printed wiring. There is. A magnetoresistive element 15 is attached to the magnetic pole surface of the magnet 11, and a lead wire or a lead frame connected to the electrode is connected to a printed wiring on a terminal board 14.

A thick cylindrical non-magnetic structure 16 is fitted inside the magnetic case 10, and a rotating shaft 20 made of a non-magnetic material supported by bearings 18 and 19 is rotatably inserted into the through hole 17 of the structure 16. It is attached to the shaft.

A permanent magnet 21 having a parallelogram cross section and having magnetic poles arranged in the axial direction is fixed to the tip of the shaft 20 as shown in the figure, and the rotation of the shaft 20 changes the magnetic flux density acting on the magnetoresistive element 15. The cover plate 22 is fixed to the magnetic case 10 or the non-magnetic structure 16 with screws (not shown).

The cover plate 22 and the magnetic case 10 function as an electromagnetic shield and also function as a magnetic path for the magnets 11 and 21. The magnet 21 is fixed to the rotating shaft 20 by cutting off the tip of the shaft 20 into a U-shaped cross section as shown in FIG. 5, and pasting the magnet 21 with an adhesive such as epoxy.

In this way, the adhesive area becomes large and the magnet 21
Since it is pasted in such a way that it is hugged from both sides, it is firmly fixed. Magnet 2 in a plane perpendicular to the rotation axis of the rotating shaft 20
As shown in FIG. 6, when the magnetoresistive element 15 is configured as an annular three-terminal element, the area of
, 15b, for example, is selected to be sufficiently larger than 15a.

One side of the parallelogram magnet 21 is the rotating shaft 20.
It is positioned so as to pass through the rotation axis 23 of. magnet 2
The optimal design for 1 should be a rectangular cross section with one side having a semicircle diameter 2t and the other side having a semicircle radius T, as shown by the broken line in FIG. Note that a power source is connected between the terminal electrodes 24 and 25 in the magnetoresistive element 15, and an output is drawn from the terminal electrode 26.

In the above configuration, when the rotary shaft 20 is rotated, the rectangular magnetic pole surface of the magnet 21 shown by the broken line in FIG. 1 applies magnetic flux B2 to the magnetoresistive element 15.

As shown by curve b in FIG. When the magneto-resistance element 15 rotates, the movement of the magnetic flux that the magnetoresistive element 15 receives has good cutting of the magnetic flux, in other words, it faithfully reproduces the rotation of the rotary shaft 20. When the magnet 21 having such a shape is used, , magnetoresistive element 15
As shown in FIG. 3b, an output with extremely excellent linearity with respect to the rotation angle θ of the shaft 20 can be obtained.

The above characteristics are the same even if the magnet 11 installed on the substrate 12 is replaced with a magnetic piece.

Further, in FIG. 1, the magnets 21 and 11 have different magnetic properties facing each other to form an attractive mode, but they may have the same magnetic poles facing each other. In this case, the magnetoresistive element 15 includes a magnet 21 that moves due to the rotation of the rotating shaft 20 and a magnet 1 that is fixed to the substrate 12.
The portion where magnet 11 forms a repulsion magnetic field is not affected by the effective magnetic flux, and the other portions are affected by the effective magnetic flux from the magnet 11. When the magnets 11 and 21 are arranged in an attractive relationship as described above, the magnet 11 always applies a bias magnetic field to the magnetoresistive element 15, so that two of the magnetoresistive elements
Considering the multiplication characteristic, a portion with a large change in magnetic resistance is used, resulting in a highly efficient output.

As described above, in the present invention, since the magnet is attached to the rotating shaft, the spread of the magnetic flux acting on the magnetoresistive element is small, unlike in the case of a magnetic piece, and the magnetic pole on the side facing the magnetoresistive element is arranged on a parallelogram. Because it is configured in a shape, it is possible to make the rise of the magnetic flux acting on the magnetoresistive element sharp at the edge of the magnetic pole, and to apply a magnetic field with uniform magnetic flux density to the magnetoresistive element, so that it is possible to make a straight line from the magnetoresistive element. It is possible to obtain output with extremely good performance.

In addition, in the potentiometer of the present invention, since the magnet fixed to the rotating shaft is used as a rectangular parallelepiped, it can be used as a large cut-out magnet, instead of being processed into a semicircular magnet as in the conventional case. Since it is not necessary, there is less loss of material (when machining a semicircle, the other half of the cut is discarded), and the cost advantage increases.

[Brief explanation of the drawing]

Figure 1 is a diagram of the shape of the magnetic field obtained from a magnet fixed to a rotating shaft, comparing the present invention and the conventional example, Figure 2 is a distribution diagram of the magnetic flux density of the magnet in Figure 1, and Figure 3 is the present invention example and the conventional example. Output voltage characteristic diagram against rotation angle of rotating shaft comparing examples,
FIG. 4 is a sectional view of the potentiometer of the present invention, FIG. 5 is a plan view showing the relationship between the rotating shaft and the magnet of the present invention, and FIG. 6 is a schematic diagram showing the relationship between the magnetic resistance element and the magnetic pole surface of the magnet. be. In the figure, 10 is a magnetic case, 11 and 21 are magnets, 12 is a substrate, 15 is a magnetic resistance element, and 20 is a rotating shaft.

Claims (1)

[Claims] 1. A permanent magnet with a parallelogram-shaped magnetic pole plate is fixed to the tip of a rotating shaft, and when the shaft is rotated, a magnetic field with a large change in magnetic flux density is applied to a magnetoresistive element placed close to the magnetic pole surface. Potentiometer configured.