JP2002213992A - Noncontact magnetic measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncontact magnetic measuring instrument capable of compensating temperature over a wide temperature range and reduced in manufacturing cost. SOLUTION: The noncontact magnetic measuring instrument 10 is provided with a permanent magnet f for measurement and a magnetic field detecting element d for measurement, which are mutually relatively displaced similar to prior arts, and also has a magnetic field detecting element (a) for temperature compensation for outputting an electrical signal corresponding to an external magnetic field, a permanent magnet e for temperature compensation provided adjacent to the magnetic field detecting element (a), an amplifier b in which the magnetic field detecting element (a) for temperature compensation and a reference voltage Vref are connected to an input side and the magnetic field detecting element d for measurement is connected to an output side, and which amplifies an input signal and supplies a voltage to the magnetic field detecting element d for measurement, and a temperature compensation circuit which constitutes a negative feedback by using the output amplified by the amplifier b as a supply power for the magnetic field detecting element (a) for temperature compensation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact magnetic measuring device such as a non-contact magnetic potentiometer and an encoder incorporating a magnetic field detecting element such as a Hall element and a magneto-resistive element, and more particularly to a non-contact magnetic measuring device in a wide temperature range. The present invention relates to a non-contact magnetic measurement device capable of compensating for temperature (that is, eliminating a temperature error).

[0002]

2. Description of the Related Art As a simple and inexpensive method for detecting a magnetic field intensity, a method using a Hall element or a magnetoresistive element has been widely used. This method uses a function in which the Hall element generates a voltage according to the strength of the magnetic field, and a function in which the magnetoresistive element changes the electric resistance according to the strength of the magnetic field.

[0003] By utilizing these functions of a Hall element or a magnetoresistive element and combining them with a permanent magnet, the amount of change in rotation angle, distance, or the like, or the rate of change in rotation speed, moving speed, or the like can be measured in a non-contact manner. A non-contact magnetic measuring device, such as a non-contact magnetic potentiometer or an encoder, which performs measurement by using the method described above, can be configured.

FIGS. 3 to 6 show the schematic structure of these non-contact magnetic measuring devices.

That is, as shown in FIG. 3, a rotary type non-contact magnetic potentiometer comprises a rotary rod 1 to which angular displacement of a rotary shaft in a measuring object such as a steering wheel, an accelerator (not shown) is transmitted, and this rotary rod. 1 is a disk-shaped permanent magnet for measurement 2 in which one semicircular portion is an N pole and the other semicircular portion is an S pole, a Hall element disposed near the permanent magnet 2 for measurement, and a magnetoresistance. The main part is constituted by the measurement magnetic field detecting element 3 such as an element.

The positional relationship between the measuring magnetic field detecting element 3 and the measuring permanent magnet 2 changes with the rotation of the rotating rod 1 to which the angular displacement of the rotating shaft of the object to be measured is transmitted. Since the magnetic field intensity detected by the measurement magnetic field detection element 3 also changes due to the change in the measurement, the change amount (rotation angle) of the measurement target such as the steering wheel and the accelerator, based on the output signal from the measurement magnetic field detection element 3, The change speed (rotation speed) can be measured.

[0007] Instead of the disk-shaped permanent magnet for measurement 2, as shown in FIG. 4, a rotary type non-contact magnet in which a permanent magnet for measurement 4 whose thickness dimension continuously changes in the rotational direction is incorporated. Type potentiometers are also known.

Further, the linear non-contact magnetic potentiometer includes a measuring magnetic field detecting element 5 such as a Hall element and a magnetoresistive element attached to a measuring object (not shown) which linearly displaces in a direction indicated by a dashed line. The main part thereof is constituted by a belt-shaped measurement permanent magnet 6 which is arranged in the displacement direction of the measurement object and whose thickness dimension continuously changes (see FIG. 5).

In this linear non-contact magnetic potentiometer, the distance (d) between the magnetic field detecting element 5 for measurement and the permanent magnet 6 for measurement is also changed with the displacement of the object to be measured.
1, d2) changes, and the magnetic field intensity detected by the magnetic field detecting element 5 for measurement also changes due to this change. It is possible to measure the amount (distance) and the changing speed (moving speed).

In place of the strip-shaped permanent magnet for measurement 6, a permanent magnet for measurement 7 whose thickness is constant and whose width continuously changes in the length direction is incorporated as shown in FIG. Linear non-contact magnetic potentiometers are also known.

[0011]

The non-contact magnetic measuring devices such as non-contact magnetic potentiometers and encoders have a longer operating life than non-contact measuring devices because they are non-contact. It has advantages such as low rotation torque or friction, excellent high-speed response, no sliding arc and explosion-proof properties, but it also has the following disadvantages.

That is, the magnetic field detecting element for measurement such as the Hall element and the magnetoresistive element and the permanent magnet for measurement have a large temperature dependency, and due to this, the magnetic field detecting element for measurement and the permanent magnet for measuring are incorporated. Non-contact magnetic potentiometers, non-contact magnetic measuring devices such as encoders also have temperature dependence, so measurement accuracy, that is, there is a problem that the linearity of the electrical signal output with respect to the angle and distance of the measurement target is inferior. I was

As a method for correcting the temperature characteristics of the non-contact magnetic measuring device, a method using a thermistor,
Methods using a plurality of measurement magnetic field detection elements and the like have been proposed and put into practical use, but it is difficult to perform temperature compensation over a wide temperature range with these methods.
Over the assumed temperature range (for example, minus 40 degrees Celsius to plus 125 degrees Celsius) in the car where the accelerator etc. is installed,
It was difficult to make the error of linearity including temperature dependency within ± 1%.

In the specification of Japanese Patent Application No. 11-2677782, two Hall elements 31 and 32 for measurement whose positional relationship is fixed are provided at positions where the magnetic field strength of the permanent magnet 2 for measurement is different. Discloses a non-contact magnetic measurement device (see FIG. 7) in which excellent temperature compensation is achieved by using a quotient of output voltages from the Hall elements 31 and 32 for output as an output signal, but a circuit for calculating the quotient. The expensive (for example, a divider or a microcomputer) has been a practical obstacle.

The present invention has been made in view of such problems, and it is an object of the present invention that temperature compensation can be performed over a wide temperature range (that is, temperature errors are eliminated) and manufacturing cost is reduced. It is another object of the present invention to provide a non-contact magnetic measuring device capable of reducing the amount of noise.

[0016]

In other words, the invention according to claim 1 comprises a magnet for measurement and a magnetic field detecting element for measurement which are relatively displaced from each other, one of which is attached to the object to be measured, An electric signal corresponding to an external magnetic field is assumed on the premise of a non-contact magnetic measuring device that measures the change amount or the change speed of the measurement object based on an output signal based on the magnetic field strength of the measurement magnet body detected by the magnetic field detecting element for measurement. A temperature compensating magnetic field detecting element to be output, a temperature compensating permanent magnet provided near the magnetic field detecting element, a temperature compensating magnetic field detecting element and a reference voltage connected to the input side, and a measuring magnetic field connected to the output side. An amplifier connected to the detecting element and amplifying an input signal to supply a voltage to the magnetic field detecting element for measurement; and outputting an output amplified by the amplifier to the magnetic field for temperature compensation. Temperature compensation circuit which constitutes the negative feedback by the supply power of the detecting element, characterized in that is provided.

Further, the invention according to claim 2 is based on the non-contact magnetic measuring device according to the invention according to claim 1, and the following relational expression (5) showing the output (Ve) amplified by the amplifier: The amplification factor Ab of the amplifier is set so as to satisfy the condition of 1 << ka (T) · Ab,
The temperature characteristics of the temperature compensating magnetic field detecting element and the measuring magnetic field detecting element are equal or substantially equal, and the temperature characteristics of the temperature compensating permanent magnet and the measuring magnet body are set equal or substantially equal. Ve = Ab · Vref / [1 + ka (T) · Be · Ab] (5) where the sensitivity of the magnetic field detecting element for temperature compensation as a function of the temperature T is ka (T), the reference voltage is Vref, The magnetic field received by the compensating magnetic field detecting element from the temperature compensating permanent magnet is B
e.

The invention according to claim 3 is the invention according to claim 1 or 2
Assuming a non-contact magnetic measuring device according to the described invention,
It has two magnetic field detecting elements for temperature compensation and multiple magnetic field detecting elements for measurement, and the supply voltage to each magnetic field detecting element for measurement is obtained by amplifying the output of the magnetic field detecting element for temperature compensation. I do.

Further, the invention according to claim 4 is based on claim 1,
The invention according to claim 5, wherein the non-contact magnetic measuring device according to the invention described in (2) or (3) is premised on that the temperature detecting magnetic field detecting element and the measuring magnetic field detecting element are constituted by Hall elements. Is characterized in that the magnetic field detecting element for temperature compensation and the magnetic field detecting element for measurement are constituted by magnetic resistance elements.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic explanatory view showing an example of a circuit configuration of a non-contact magnetic measuring device 10 according to the present invention.

That is, the non-contact magnetic measuring device 10
Comprises a permanent magnet f for measurement and a magnetic field detecting element d for measurement, which are displaced relative to each other as in a conventional non-contact magnetic measuring apparatus, and a magnetic field detecting element for temperature compensation for outputting an electric signal corresponding to an external magnetic field. a, a temperature compensating permanent magnet e provided near the magnetic field detecting element a, the temperature compensating magnetic field detecting element a and the reference voltage Vref connected to the input side, and the measuring magnetic field detecting element d to the output side. And an amplifier b for amplifying an input signal and supplying a voltage to the magnetic field detecting element d for measurement, and supplying an output amplified by the amplifier b to power supplied to the magnetic field detecting element a for temperature compensation. Thus, a temperature compensation circuit forming a negative feedback is provided.

In FIG. 1, g denotes an output amplifier to which a measuring magnetic field detecting element d is connected and which amplifies an electric signal corresponding to the measuring magnet f. The Hall element and the magneto-resistive element described above are generally applied to the magnetic field detecting element d for measurement and the magnetic field detecting element a for temperature compensation. Is applicable as long as is obtained.

The non-contact magnetic measuring device 10
However, the principle of enabling temperature compensation over a wide temperature range will be described below.

First, it is assumed that the sensitivities kd and ka of the measuring magnetic field detecting element d and the temperature compensating magnetic field detecting element a having temperature dependency are respectively set as ka = ka as a function of the temperature T.
(T), kd = kd (T), the voltage amplification factors of the amplifiers b and g are Ab and Ag, and the reference voltage is Vref.

Assuming that the magnetic field received by the temperature compensating magnetic field detecting element a from the temperature compensating permanent magnet e is Be, Be = Bec · Be (T) (1) where Bec in the relational expression (1) is a constant. , Be (T) are functions of the temperature T.

Similarly, assuming that the magnetic field received by the measurement magnetic field detecting element d from the measurement permanent magnet f is Bf, Bf = Bfc · Bf (T) · g (x) (2) In the relational expression (2), Bfc is a constant, Bf (T) is a function of temperature T, and g (x) is a function of angle and position.

Here, the signal Va from the temperature compensating magnetic field detecting element a is the magnetic field Be received by the temperature compensating magnetic field detecting element a from the temperature compensating permanent magnet e, and the voltage supplied to the temperature compensating magnetic field detecting element a. Since it is proportional to Ve, it can be expressed as Va = ka.Be.Ve (3).

Looking at the input / output relationship at the amplifier b, the output Va from the temperature compensating magnetic field detecting element a is amplified by the amplifier b, and the amplified output Ve is supplied to the temperature compensating magnetic field detecting element a. Since the negative feedback is constituted by the power, Ve = Ab · [Vref−Va] = Ab · [Vref−ka (T) · Be · Ve] (4) From this relational expression (4), Ve = Ab · Vref / [1 + ka (T) · Be · Ab] (5) Here, regarding the amplification factor Ab of the amplifier b, ka
If it is set large enough to satisfy the condition of (T) · Ab >> 1, Ve = Vref / [ka (T) · Be] (6)

The signal Vd from the measuring magnetic field detecting element d is also proportional to the magnetic field Bf received from the measuring permanent magnet f and the voltage Ve supplied to the measuring magnetic field detecting element d, so that Vd = kd · Bf -It can be expressed as Ve (7).

By substituting the relational expression (6) into the relational expression (7) and the relational expression (2), Vd = kd (T) （Bf ・ Vref / [ka (T) ・ Be] = kd (T ) · Bfc · Bf (T) · g (x) · Vref / [ka (T) · Bec · Be (T)] (8) Here, the temperature compensation magnetic field detection element a and the measurement magnetic field detection element d Kd (T) ≒ if the temperature compensating permanent magnet e and the measuring permanent magnet f are also composed of magnets having the same or substantially the same temperature characteristics. ka
(T), Bf (T) ≒ Be (T), so that Vd = Bfc · g (x) · Vref / Bec (9) where Bfc and Bec are the shape of the permanent magnet, the arrangement with the magnetic field detecting element, and the like. From the above relational expression (9)
It can be confirmed that d does not depend on the temperature.

Accordingly, the output Vo obtained by the measuring magnetic field detecting element d based on the magnetic field strength of the measuring permanent magnet f is as follows: Vo = Ag · Vd = Ag · Bfc · g (x) · Vref / Bec (10) It can be obtained from the relational expression (10), and it is confirmed from the relational expression (10) that Vo does not depend on the temperature.

Therefore, the above-mentioned Japanese Patent Application No. Hei 11-26778.
By applying the non-contact magnetic measuring device according to the present invention as compared with a non-contact magnetic measuring device requiring a circuit such as a divider or a microcomputer disclosed in the specification of Japanese Patent No. A signal proportional to the position can be detected at low cost and with high accuracy.

Although the non-contact magnetic measuring device according to this embodiment is constructed by incorporating a single measuring magnetic field detecting element and a single temperature compensating magnetic field detecting element, A plurality of magnetic field detecting elements may be incorporated, and the voltage supplied to each of the measuring magnetic field detecting elements may be obtained by amplifying the output of a single temperature compensating magnetic field detecting element.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary non-contact magnetic potentiometer according to an embodiment in which each magnetic field detecting element having the circuit configuration shown in FIG.

That is, as shown in FIG. 2A, the rotary type non-contact magnetic potentiometer 40 includes a rotary rod 1 to which angular displacement of a rotary shaft in a measurement object (not shown) is transmitted, and the rotary rod 1 1. A disk-shaped permanent magnet 4 mounted on 1 and having one semicircular portion as an N pole and the other semicircular portion as an S pole
1 (a permanent magnet f in FIG. 1) and a measuring magnetic field detecting element 42 such as a Hall element arranged near the permanent magnet 41.
(In FIG. 1, the magnetic field detecting element d for measurement) and the permanent magnet 4
1 and a temperature compensating magnetic field detecting element 43 (a temperature compensating magnetic field detecting element a in FIG. 1) and a temperature compensating permanent magnet 44 (a permanent magnet e in FIG. 1), which are fixedly arranged at positions sufficiently separated from each other. The main part is constituted by.

The magnetic field detecting element 42 (d) for measurement and the magnetic field detecting element 43 (a) for temperature compensation are selected from the same manufacturer and have the same model number.
1 (f) and the temperature compensating permanent magnet 44 (e) are also selected from the same material from the same manufacturer.

FIG. 2B is a graph showing the relationship between the angular displacement (θ) and the signal output (Vo) in the rotary non-contact magnetic potentiometer.

When the error of the output signal (Vo) at an angular displacement (θ) of −40 ° C. and 125 ° C. was measured with reference to the signal output at 25 ° C., a maximum of + 0.4% at −40 ° C. and 125 ° C. Only a small error of -0.3% was confirmed.

COMPARATIVE EXAMPLE A Hall element 21 is applied as a magnetic field detecting element, and a circuit as shown in FIG.
A rotary non-contact magnetic potentiometer similar to the conventional one shown in FIG. 3 was constructed.

Then, as a result of performing the same measurement as in the example, the error of the output signal (Vo) at an angular displacement (θ) of −40 ° C. and 125 ° C. was measured with reference to the signal output at 25 ° C. Up to + 2.4% at 40 ° C, 12
At 5 ° C., a large error of −9.3% was confirmed.

As a result, the superiority of the rotary non-contact magnetic potentiometer according to the example was confirmed as compared with the rotary non-contact magnetic potentiometer according to the comparative example.

[0043]

According to the non-contact magnetic measuring device according to the first to fifth aspects of the present invention, a magnetic field detecting element for temperature compensation for outputting an electric signal corresponding to an external magnetic field, The provided temperature compensating permanent magnet, the temperature compensating magnetic field detecting element and the reference voltage are connected on the input side, and the measuring magnetic field detecting element is connected on the output side, and the input signal is amplified to amplify the input signal. An amplifier that supplies a voltage to the detection element, and a temperature compensation circuit that forms negative feedback by using the output amplified by the amplifier as the power supplied to the temperature compensation magnetic field detection element. The temperature dependency of the magnetic field detection element is eliminated without incorporating a circuit such as a divider or microcomputer, and the amount or speed of change of the measurement object can be measured with high accuracy over a wide temperature range. With a kill effect.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of a circuit configuration of a non-contact magnetic measuring device according to the present invention.

FIG. 2A is an explanatory view showing a schematic configuration of a rotary non-contact magnetic potentiometer according to an embodiment;
(B) is a graph showing the relationship between the angular displacement θ and the signal output V0 in the rotary non-contact magnetic potentiometer.

FIG. 3 is an explanatory diagram showing a schematic configuration of a rotary non-contact magnetic potentiometer according to a conventional example.

FIG. 4 is an explanatory diagram showing a schematic configuration of a rotary non-contact magnetic potentiometer according to another conventional example.

FIG. 5 is an explanatory view showing a schematic configuration of a linear non-contact magnetic potentiometer according to a conventional example.

FIG. 6 is an explanatory diagram showing a schematic configuration of a linear non-contact magnetic potentiometer according to another conventional example.

FIG. 7 is an explanatory diagram showing a schematic configuration of a conventional improved rotary non-contact magnetic potentiometer that uses a quotient of output voltages from two Hall elements as an output signal.

FIG. 8 is an explanatory diagram showing a circuit configuration of a magnetic field detecting element incorporated in a rotary non-contact magnetic potentiometer of a comparative example.

[Explanation of symbols]

 10 Non-contact magnetic measuring device a Magnetic field detecting element for temperature compensation b Amplifier d Magnetic field detecting element for measurement e Permanent magnet for temperature compensation f Permanent magnet for measurement Vref Reference voltage

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G01R 33/09 G01B 7/30 101B // G01B 7/00 G01R 33/06 H 7/30 101R F term (reference) 2F063 AA02 AA35 BA08 CB01 CC05 CC06 DA05 DD03 EA02 EA03 GA52 KA01 KA02 LA30 2F077 AA13 CC02 CC08 JJ02 JJ03 JJ08 JJ09 JJ23 NN17 NN24 PP12 PP14 TT82 UU09 UU10 UU11 2G017 A05AD05 AC05 BA05 AC05

Claims (5)

[Claims] A magnetic field of a measuring magnet body which is provided with a measuring magnet body and a measuring magnetic field detecting element which are relatively displaced from each other, one of which is attached to a measuring object, and which is detected by the measuring magnetic field detecting element. In a non-contact magnetic measuring device for measuring a change amount or a change speed of the object to be measured by an output signal based on intensity, a magnetic field detecting element for temperature compensation for outputting an electric signal corresponding to an external magnetic field, and a vicinity of the magnetic field detecting element The temperature compensating permanent magnet provided on the input side, the temperature compensating magnetic field detecting element and the reference voltage are connected to the input side, and the measuring magnetic field detecting element is connected to the output side, and the input signal is amplified to amplify the input signal. An amplifier that supplies a voltage to the magnetic field detecting element, and the output amplified by the amplifier is used as the power supplied to the magnetic field detecting element for temperature compensation to provide negative feedback. A non-contact magnetic measuring device comprising a temperature compensation circuit. 2. In the following relational expression (5) showing the output (Ve) amplified by the amplifier, 1 << ka (T) · Ab
The amplification factor Ab of the amplifier is set so as to satisfy the following condition, and the temperature characteristics of the magnetic field detecting element for temperature compensation and the magnetic field detecting element for measurement are equal or substantially equal, and
2. The non-contact magnetic measuring device according to claim 1, wherein the temperature characteristics of the temperature compensating permanent magnet and the measuring magnet are set to be equal or substantially equal. Ve = Ab · Vref / [1 + ka (T) · Be · Ab] (5) where the sensitivity of the temperature compensation magnetic field detecting element as a function of the temperature T is ka (T), the reference voltage is Vref, and the temperature compensation is The magnetic field which the magnetic field detecting element receives from the temperature compensating permanent magnet is B
e. 3. A magnetic field detecting element for temperature compensation and a plurality of magnetic field detecting elements for measurement are provided, and all voltages supplied to the magnetic field detecting elements for measurement are obtained by amplifying the output of the magnetic field detecting element for temperature compensation. The non-contact magnetic measuring device according to claim 1 or 2, wherein: 4. The non-contact magnetic measuring device according to claim 1, wherein the temperature compensating magnetic field detecting element and the measuring magnetic field detecting element are constituted by Hall elements. 5. The non-contact magnetic measuring device according to claim 1, wherein the temperature compensating magnetic field detecting element and the measuring magnetic field detecting element are constituted by magnetoresistive elements.