JPS6295402A - Rotational angle detector - Google Patents

Abstract

PURPOSE:To measure an angle with extremely high precision by arranging two Hall elements at a proper mutual angle. CONSTITUTION:The two Hall elements 9 and 10 are fixed in the gap between magnets 7 and 8 while having magnetic flux sensitive surfaces 9a and 10a at 90 deg. to each other, and angles of theta and theta-90 deg. of magnetic flux penetrating the two Hall elements 9 and 10 vary through the rotation of a rotating shaft 5. Further, feeders 11a and 11b and signal lines 12a and 12b are connected to the Hall elements 9 and 10 respectively and the current from a current supply circuit 13 is supplied to the Hall elements 9 and 10 through the feeders 11a and 11b. A microprocessor 15 calculates the angular displacement theta of the rotating shaft from the signals from the Hall elements 9 and 10 and the angular displacement is converted by a D/A converter 19 into an analog value, which is sent out.

Description

[Detailed description of the invention] Detailed theory of 3 shots 1j1 151 [Industrial usage? ] Unreleased II relates to a rotation rQ degree detection function that can be used for a liquid level gauge, temperature 51, pressure gauge, etc.

[Conventional technology]

Conventionally, various devices have been used to detect the displacement angle of rotating parts such as the rotating parts of liquid level gauges, bimetallic thermometers, pressure, and Bourdon tubes. There is one using a Hall element as shown below.

This is the rotation u (with 11 Hall elements 4 in the magnetic flux 3 created by a pair of magnets 1 and 2) Lt
Element 4 (7) 'A Ijl 4 a d11
East v: If B, when a magnetic flux at an angle of 0 with the magnetically sensitive surface 4d is applied and a current I is applied to the power supply terminal, E=Ni・B・B 5InO@II fight ( 1) K: Uses the fact that an electromotive force E proportional to 0, which is a proportionality constant, is generated.

Therefore, as shown in FIG. 5, rotatable magnets 1 and 2 are provided outside the Hall element so that the angle 0 with the magnetically sensitive surface 4a is variable and the magnetic flux density B on the magnetically sensitive surface is constant. Accordingly, a non-contact angle detector can be obtained.

Such an angle detector has a simple structure, can be made small, and is inexpensive, but as can be seen from equation (1) above,
There is a drawback that when the magnetic flux density IffB changes, the output (/iE) is affected.

By the way, magnets currently in practical use can be broadly classified into the following three types.

a, rare earth magnet b, ferrite magnet C alnico magnet Among these, b has a large magnetic flux density B that changes depending on the temperature [11]. Further, although C has a very small change in magnetic flux density due to temperature, B may become small due to demagnetization due to external magnetism. Since magnet a is less affected by temperature than b and has almost no demagnetization, the angle detector shown in Fig. 4 can be put to practical use by using magnet a, but in a wide temperature range, the temperature change of B is Therefore, it is difficult to obtain a highly accurate detector.

[Problem that the invention seeks to solve]

In the present invention, the electromotive force of the Hall element is 51n of the penetrating magnetic flux angle.
E [, i L, which is proportional to O, is obtained by providing two Hall elements whose magnetic flux-sensitive surfaces are shifted by 90 degrees from each other, and by taking the ratio of these two electromotive forces, accuracy that is not affected by changes in magnetic flux density can be obtained. Enables high angle detection.

[Means for solving problems]

The rotation angle detector of the present invention includes a pair of magnets that are attached to the rotation axis of a rotating body and are rotatable with each rotation of the rotation axis, and are arranged so as to face each other, and a magnetic flux sensitive surface is provided between the magnets. Two Hall elements -r are provided which are shifted by an appropriate deflection angle, and the rotation angle of the rotating body is detected by the ratio of two electromotive forces generated by magnetic flux passing through the Hall elements for 1τ.

[Effect]

With the angular displacement of the rotating body, the penetrating magnetic flux angle of the two Hall elements arranged with a phase difference of 80 degrees changes, and the displacement of the rotating body is determined by the ratio of the electromotive force of each Hall element generated thereby. Detect angle.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained in detail with reference to a specific example shown in the accompanying drawings.

In FIG. 1.2, a U-shaped yoke 6 is connected to the tip of a rotating shaft 5 that is connected to an object to be measured, a rotating body (not shown) that changes angle.

A pair of magnets 7.8 with N and S facing each other are attached to the end of the yoke 6.

The magnetic flux from magnet 7 reaches magnet 8.

There are two Hall elements 9.1 in the gap between magnets 7 and 8.
0 is fixed by shifting the magnetic flux sensitive surface 9a; It's about to change.

In addition, power supply lines 11a and 11b and signal lines 12a and +2b are connected to the Hall element 9.10, respectively, and as shown in FIG. J: -f 9, is designed to be supplied to lO.

In addition, signal lines from halls 9 and 10! 2a, 12
b is connected to the amplification circuit, and the amplified voltage value is latched into the sample and hold circuit 1B by a control signal from the microprocessor 15, and the latched signal is sequentially converted to A/'D by the multiplexer 17.
The signal is input to the microprocessor 15 via the converter 18. In the microprocessor 15, each Hall element 9.
The angular displacement 0 of the rotating shaft is calculated from the signal from 10, converted into analog 5 by the D/A converter 19, and sent.

Next, the principle of operation of the unreleased 151 will be described. In FIG. 2, if the angle between the magnetic flux sensitive surface of the Hall element 9 and the core flux 3 is 0, then from equation (1) in ii'ij, the Hall element 9
Ez=2・I2・B・5 between the output terminals A2 and B2 of
An output voltage of 1nO-.ellll (2) K2: proportionality constant B: magnetic flux density is generated.

On the other hand, since the magnetic flux sensitive surfaces of the Hall element 10 are shifted by 90", E1=K(・Il
e B −gin(90” −0)=K16+,・B
-cosOe a a... (3) An output voltage of 1: proportionality constant is generated.

Therefore, from equations (2) and (3), the following equation holds true.

In other words, since B is eliminated from the equation, if the angle is calculated by finding the ratio of the output voltages E1 and K2 of the two Hall elements, the angle becomes irrelevant to the magnetic flux density B of the magnet, even if B changes. The angle can also be detected with high precision.

Note that if the denominator of equation (4) or (5) is significantly smaller than the numerator, it is undesirable in terms of calculation accuracy, so K2<
If <El, then equation (5) should be used, and if K2>>El, equation (4) should be used.

To finally find 0, use tan O or coto
Since it is necessary to perform an operation to obtain O from the above, the electrical signal is converted into a digital quantity as shown in FIG. 3, and the digital operation is performed using a microprocessor or the like.

Also, in equations (4) and (5), the range of 0 is O≦0≦
The angle is 180°, but if the angle is divided into smaller sections according to the positive and negative values of El and K2 as shown in Table 1, continuous measurement from 0 to 360° can be performed.

In addition, K1 and K2 are constants specific to the Hall element, and are also affected by temperature. There will be no problem if you design the electrical circuit so that.

Table 1 [Effects of Unreleased II] As described above, according to Unreleased II, by arranging the children in the two holes so that they are shifted from each other by an appropriate angle, changes in magnetic flux due to temperature etc. and the influence of external magnetic fields are reduced. can be canceled out, making it possible to determine the angle A11l with very high accuracy.

In addition, Hall Niko consumes less power, allows the entire device to be miniaturized, and has good responsiveness to changes in magnetic flux angle, making it possible to measure angles without R deviation for one hour.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of the rotation angle detector according to the present invention, Fig. 2 is a diagram showing the angular relationship between the magnet and the Hall element, and Fig. 3 is a circuit for processing the feedback from the Hall element. FIGS. 4 and 5 are block diagrams showing the relationship between the hole J2 i'- of the conventional angle detector and the magnet. 1.2.8 in λ? -・Magnet 3...Magnetic flux 1.9.
10... Hall elements 4a, 9a, 10a - magnetic flux sensitive surface 5... rotating shaft 6... yoke 1 la, llb 11 - supply 1M, wire
12a, 12b Conflict
() Line 13... Current supply circuit 14... Amplifier 15, Microprocessor 16, Loss sample hold circuit 17111I, Multiplexer 18... A/D converter 19, Self, D/A converter 20... Bearing

Claims (1)

[Claims] A pair of magnets that are attached to the rotating shaft of the rotating body and can rotate as the rotating shaft rotates are arranged so as to face each other,
Two Hall elements whose magnetic flux-sensitive surfaces are shifted by an appropriate deviation angle are provided between the same magnets, and the rotation angle of the rotating body is detected by the ratio of the two electromotive forces generated by the magnetic flux passing through the Hall elements. A rotation angle detector characterized by: