JP2000131005A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor capable of accurately measuring analogous distance or displacement by compensating the temperature of the magnetic sensor using a semiconductor Hall element. SOLUTION: The magnetic sensor is provided with a substrate 16, semiconductor Hall element 17 arranged on the substrate surface, a magnet 19 arranged on the back side of the substrate and generating a magnetic field penetrating the semiconductor Hall element, a constant current circuit supplying the semiconductor Hall element with a constant current, a temperature sensor 18 arranged on the substrate and a zero point temperature compensation circuit for compensating the temperature characteristic of the zero point of the semiconductor Hall element according to the temperature detected with this temperature sensor. The sensitivity temperature coefficient of the semiconductor Hall element and the resistance temperature coefficient of the input resistance of the semiconductor Hall element are set nearly equal in absolute value but different in sign.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic device for measuring a distance (or a displacement of an object) made of a magnetic material with high accuracy, for example, for detecting a bottom dead center of a stroke of a press machine. It concerns a sensor.

[0002]

2. Description of the Related Art Conventionally, an eddy current is used as a displacement sensor for detecting the bottom dead center of a stroke of a die of a press machine, measuring the parallelism of the die, or measuring the parallelism of a gear or a drum. There is a winding type high sensitivity proximity sensor. Also,
As a magnetic sensor for detecting the number of revolutions of a motor, a sensor using a semiconductor Hall IC (integrated circuit) is also known.

[0003]

However, for example, the above-mentioned press machine is operated 3000 times per minute (3000 Strokes PerMinut).
e) If the press is performed at a high speed, the output of the wound type high-sensitivity proximity sensor will be high frequency, the signal processing circuit will be complicated, and appropriate compensation for temperature changes in the surrounding environment of the sensor shall be performed. Therefore, there has been a problem that a large measurement error of about 10 to 20 μm usually occurs due to temperature drift.

In such a case, the bottom dead center position of each stroke is unavoidably compared with the last bottom dead center position to detect a deviation from the previous value, thereby performing bottom dead center monitoring. Since the method of the previous value comparison cannot accurately detect the bottom dead center position, there is a problem that the defective product cannot be detected with high accuracy.

On the other hand, in the magnetic sensor using the semiconductor Hall IC, whether the distance to an object is equal to or more than a predetermined value,
Depending on whether it is less than a certain value, only a binary output of ON or OFF (1 or 0) can be obtained, and it is impossible to measure distance and displacement in an analog manner. It was limited to rotation speed detection and the like.

The reason why analog distance measurement cannot be performed with a conventional magnetic sensor using a semiconductor Hall element is that the sensitivity and input resistance of the semiconductor Hall element have temperature characteristics (temperature drift), and that the semiconductor Hall element has a temperature characteristic (temperature drift). This is probably because temperature characteristics also exist at the zero point of the Hall element, and it is difficult to appropriately compensate for these temperature characteristics.

[0007]

SUMMARY OF THE INVENTION The present invention provides a magnetic sensor capable of measuring distance or displacement in an analog manner with high accuracy by solving the problem of temperature compensation of a magnetic sensor using the above-mentioned semiconductor Hall element. The purpose is to do.
Therefore, the magnetic sensor according to claim 1 of the present invention is a magnetic sensor that measures a distance between an object made of a magnetic material, and a substrate, a semiconductor Hall element arranged on a surface of the substrate, A magnet arranged on the back side to generate a magnetic field penetrating the semiconductor Hall element, a constant current circuit for supplying a constant current to the semiconductor Hall element, a temperature sensor arranged on the substrate, and detection by the temperature sensor A zero-point temperature compensating circuit for compensating for the temperature characteristic of the zero point of the semiconductor Hall element according to the temperature to be applied.The sensitivity temperature coefficient of the semiconductor Hall element, the resistance temperature coefficient of the input resistance of the semiconductor Hall element, Are set so that the positive and negative signs are opposite to each other and their absolute values are substantially equal. Making the absolute value of the sensitivity temperature coefficient and the absolute value of the resistance temperature coefficient of the input resistance substantially equal depends on the impurities (for example, silicon and selenium) mixed in the process of growing the semiconductor crystal during the manufacture of the semiconductor Hall element. It can be performed by appropriately adjusting the concentration. That is, when the impurity concentration is changed (for example, 10 ^{15 to} 10 ²⁰ / cm ³⁾
Although the sensitivity temperature coefficient and the resistance temperature coefficient both change, the absolute value of the sensitivity temperature coefficient and the absolute value of the resistance temperature coefficient can be made substantially equal when a certain impurity concentration is selected.

As shown in FIG. 1, the sensitivity K of a semiconductor Hall element usually has a negative temperature characteristic that decreases at a substantially constant rate as the temperature T increases. Here, assuming that the sensitivity at the reference temperature T ₀ is K ₀ , the sensitivity change with respect to the temperature change ΔT from T ₀ is ΔK, and the sensitivity temperature coefficient is β, β = ΔK / (K ₀ · ΔT) [unit: 1 / ° C. ] ... (1)

On the other hand, as shown in FIG. 2, the input resistance R of the semiconductor Hall element has a positive temperature characteristic that increases at a substantially constant rate as the temperature T increases. The input resistance of the semiconductor Hall element at the reference temperature T ₀ is R ₀ , the input resistance change relative to the temperature change ΔT from T ₀ is ΔR, and the resistance temperature coefficient is α.
Then, α = ΔR / (R ₀ · ΔT) [unit: 1 / ° C.] (2)

In FIG. 3, it is assumed that a constant current I is supplied from a constant current circuit 2 to an input terminal of a semiconductor Hall element 1 and an input resistance at a temperature T (= T ₀ + ΔT) is R (=
R ₀ + ΔR), the input voltage of the semiconductor Hall element 1 is V _IN ,
Let the sensitivity be K (= K ₀ + ΔK). When the magnetic flux density of the bias magnetic field applied to the semiconductor Hall element 1 from a magnet (not shown) is B, and the temperature drift of the zero point of the semiconductor Hall element 1 at the temperature T is V _Z (T), the semiconductor Hall element at the temperature T The output voltage V _{OUT of} 1 is as follows: V _OUT = K · B · V _IN + V _Z (T) = K · B · I · R + V _Z (T) = (K ₀ + ΔK) · (R ₀ + ΔR) · B · I + V _Z (T) ... (3)

From the above equations (1) and (2), ΔK = β · K ₀
· [Delta] T, since it is _{ΔR = α · R 0 · ΔT} , when these are substituted into Equation _{(3), V OUT = K} 0 · (1 + β · ΔT) · R 0 · (1 + αΔT) · B · I + V Z (T ) = K ₀ · R ₀ · B · I · (1+ (α + β) · ΔT + α · β · ΔT ² ) + V _Z (T) (4)

Here, in the present invention, the semiconductor Hall element 1
Since the absolute value of the temperature coefficient of sensitivity β (negative value) and the absolute value of the temperature coefficient of resistance α (positive value) are set to be substantially equal,
(Α + β) ≒ 0 in equation (4). Α, β
Are sufficiently small and close to 0, and can be approximated to α · β · ΔT ² ≒ 0 in equation (4). Substituting these into equation (4) results in V _OUT ≒ K ₀ · R ₀ -BI + _VZ (T) ... (5)

Since K ₀ · R ₀ · B · I in the equation (5) is constant irrespective of the temperature change, the output voltage V _OUT of the semiconductor Hall element 1 of the present invention has a zero point temperature drift V _OUT. Only the compensation for _Z (T) needs to be performed. Specifically, in the zero-point temperature compensating circuit 3 of FIG. 3, the output voltage V _OUT of the semiconductor Hall element 1 is equal to the voltage −V having the opposite sign to the temperature drift V _Z (T) and having the same absolute value.
_Z (T) may be added.

According to a second aspect of the present invention, in the magnetic sensor according to the first aspect, the semiconductor Hall element is formed of a semiconductor having a substantially linear temperature characteristic at a zero point.

In FIG. 4, a zero-point temperature drift V _Z (T) exists in the output voltage V _OUT of the semiconductor Hall element 1, and this V _Z (T) rises due to manufacturing variations. May decrease in some cases, and may increase in some cases. Hereinafter, a case in which the temperature T decreases as the temperature T increases will be described as an example. As shown by the straight line V _OUT in the figure, if the distance to the object is constant, the temperature T
In fact, the output voltage of the semiconductor Hall element 1 which should be constant regardless of the temperature T.sub.Z (T) as shown by the straight line _V.sub.OUT (T) due to the existence of the temperature drift _V.sub.Z (T) at the zero point.
Decrease with the rise of Accordingly, as described above, the output V of the semiconductor Hall element 1 is
_It is necessary to add −V _Z (T) to _OUT (T).

In this case, as shown by V _Z (T) in FIG.
If the temperature characteristic of the zero point changes substantially linearly in accordance with the change in the temperature T, the temperature compensation in the zero point temperature compensating circuit 3 becomes substantially linear as the temperature T increases, as shown in FIG. since it is only adding the -V _Z (T) which increases, so that perform the temperature compensation with ease and high accuracy.

According to a third aspect of the present invention, there is provided the magnetic sensor according to the second aspect, wherein the semiconductor is gallium arsenide.

The present inventor has found through experiments that the temperature characteristic of the zero point of a Hall element made of gallium arsenide is substantially linear. Here, while applying a bias magnetic field to the Hall element made of gallium arsenide and supplying a constant current, the temperature is changed from 0 ° C. to 50 ° C. in steps of 10 ° C.,
Table 1 and FIG. 6 show the results of measuring the relationship between the distance between the Hall element and the object (magnetic material) and the output voltage at each temperature.

[0019]

[Table 1]

As is clear from each of the six curves in FIG. 6, the output voltage decreases as the distance increases. When the six curves are compared with each other, it can be seen that the output voltage decreases as the temperature increases, but the six curves at each temperature are substantially parallel to each other and at substantially equal intervals. In addition,
The relationship between the temperature and the output voltage at a distance of 1000 μm is as shown in FIG. 7, and the ratio of the change in the output voltage to the change in the temperature is substantially constant. V _OUT (T) in FIG.
As apparent from the relationship between V.sub.Z and _V.sub.Z (T), this means that the temperature characteristic of the zero point of the semiconductor Hall element made of gallium arsenide is substantially linear.

Next, as comparative examples, Table 2 and FIG. 8 show the results of performing the same measurement as in FIG. 6 from 0 ° C. to 60 ° C. in steps of 10 ° C. for a Hall element made of indium antimony (InSb). As is clear from FIG. 8, for the Hall element made of indium antimony, although the seven curves at each temperature are substantially parallel, the temperature characteristics at the zero point of the Hall element are not linear but are substantially linear. Therefore, the temperature compensation at the zero point becomes more complicated than that of gallium arsenide.

[0022]

[Table 2]

The magnetic sensor according to claim 4 is the magnetic sensor according to claims 1 to 3.
In any of the above configurations, by providing the inner case made of a magnetic material so as to cover the periphery of the magnet, magnetic lines of force extending from the magnet to the inner case through the semiconductor Hall element are formed. Is what you do.

A magnetic sensor according to a fifth aspect of the present invention is the magnetic sensor according to the fourth aspect, wherein an outer case made of a non-magnetic material is provided so as to cover the periphery of the inner case.

The magnetic sensor according to claim 6 is the magnetic sensor according to claims 1 to 5
Wherein the magnet has a magnetic flux density of 30.
It is characterized by generating a magnetic field of 00 gauss or more.

According to a seventh aspect of the present invention, in the magnetic sensor of the sixth aspect, the magnet is a neodymium-based rare earth magnet.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 9 and 10, the magnetic sensor 10 of the present embodiment is, for example, a press machine 13 composed of an upper die 11 and a fixed lower die 12 that can be moved up and down by a lifting drive (not shown). Is used as a monitoring device for the bottom dead center of the stroke. Magnetic sensor 1
Reference numeral 0 denotes an upper die 1 which is attached to the upper end of the side surface of the lower die 12 via an L-shaped mounting bracket 14 with screws (not shown) or the like.
An L-shaped proximity body 15 (object) made of a magnetic material such as steel is attached to a corresponding position at a lower end portion of the side surface of the device 1 with a screw or the like (not shown).

The magnetic sensor 10 accompanying the raising and lowering operation of the upper mold 11
In order to prevent damage to the magnetic head 10, a predetermined vertical gap G between the magnetic sensor 10 and the proximity body 15 is set at the bottom dead center of the stroke of the
The mounting position of the magnetic sensor 10 and the proximity body 15 is determined so as to be separated (for example, 1000 μm).

The press 13 is used for manufacturing and processing, for example, an IC (integrated circuit) lead frame, a pin head of a connector for a cellular phone, and the like, and presses at a high speed of about 3000 to 4000 times per minute. Although the operation is performed, the products manufactured by the press 13 and the operation speed are not limited to those described above.

As shown in FIG. 11, the magnetic sensor 10
A disk-shaped printed board 16 made of glass fiber impregnated epoxy resin or the like is provided, and a semiconductor Hall element 17 made of gallium arsenide (GaAs) is arranged at substantially the center of the surface (upper surface) of the printed board 16. Further, on the back surface (lower surface) of the printed board 16, a temperature sensor 18 made of Si-IC or the like is arranged at a position shifted from the center to the outer peripheral side.

On the back surface side of the printed circuit board 16, a magnet 19 made of a neodymium-based rare earth magnet (a molded sintered body containing Nd-Fe-B as a main component) or the like and generating a large magnetic field having a magnetic flux density of 3000 gauss or more is provided. Are located. Magnet 1
Reference numeral 9 denotes a cylindrical small-diameter portion 19a whose upper surface is in contact with the central portion of the back surface of the printed circuit board 16, and a cylindrical large-diameter portion 19b concentrically arranged below the small-diameter portion 19a. Although FIG. 11 shows a case where the small-diameter portion 19a and the large-diameter portion 19b are integrally formed, the small-diameter portion 19a and the large-diameter portion 19b are formed into a two-piece body for convenience of manufacturing the magnet 19. You may.

In order to cover the outer side and the lower side of the magnet 19,
A bottomed cylindrical inner case 20 made of a magnetic material such as SS steel (JIS G 3101) is arranged. The upper part of the inner case 20 is opened, and the upper surface of the cylindrical side wall 20 a is joined to the outer peripheral end of the back surface of the printed circuit board 16.

The inner case 20 has a role as a magnetic circuit. Since the shape of the magnet 19 and the inner case 20 and the semiconductor Hall element 17 are arranged at the center of the magnet 19, for example, 11, the small-diameter portion 19 a of the magnet 19 above the magnetic sensor 10.
The lines of magnetic force that penetrate the semiconductor Hall element 17 from the upper surface in the thickness direction and reach the upper surface of the side wall 20a of the inner case 20 are formed, for example, as shown by a solid line S1. That is, when the distance between the magnetic sensor 10 and the proximity body 15 is relatively large, the magnetic flux density passing through the proximity body 15 is relatively small, and therefore the magnetic flux density vertically penetrating the semiconductor Hall element 17 is relatively small. .

As the upper mold 11 descends, the proximity body 15
When approaching from the solid line position in FIG. 11 to the one-dot chain line position, the magnetic force line changes, for example, as indicated by S2 shown by the one-dot chain line, and the magnetic flux density passing through the proximity body 15 increases. The magnetic flux density penetrating vertically increases, and the output voltage of the semiconductor Hall element 17 increases accordingly. In this way, the proximity object 15 is
, The output voltage of the semiconductor Hall element 17 increases, and conversely, as the proximity body 15 moves away from the magnetic sensor 10, the output voltage of the semiconductor Hall element 17 decreases.

An outer case 21 made of a non-magnetic material such as aluminum is disposed so as to cover the outer case and the lower portion of the inner case 20 and the printed circuit board 16. This outer case 2
Reference numeral 1 serves as a magnetic shield and protects the lower mold 12 to which the magnetic sensor 10 is attached from being disturbed even when the lower mold 12 is formed of a magnetic material.

In the magnetic sensor 10, as the magnet 19,
Since a magnetic field that can generate a large magnetic field of 3000 gauss or more is used, the amount of change in the magnetic field due to a change in the distance between the semiconductor Hall element 17 and the proximity body 15 is increased, so that the magnetic sensor 10 This makes it possible to detect even a slight change, so that the sensitivity of the semiconductor Hall element 17 can be increased. Since the inner case 20 serving as a magnetic circuit is arranged around the magnet 19, the magnetic field penetrating the semiconductor Hall element 17 can be further increased, and the sensitivity of the magnetic sensor 10 can be further increased. realizable. Further, since the outer case 21 made of a non-magnetic material is provided, the detection accuracy does not decrease even when there is another magnetic material around.

As is apparent from FIG.
1 is formed in a circular cross section corresponding to the outer shape of the inner case 20, while the outer periphery of the outer case 21 is formed in a flat shape corresponding to the outer shape of the lower die 12 of the press 13, for example. It is formed in a rectangular shape. The magnetic sensor 1
The size of 0 is, for example, the height H1 of the inner case 20 in FIG.
The height H2 can be about 8 mm, and the long-side direction dimension D2 can be about 30 mm. However, these values are merely examples, and the size can be appropriately changed according to the use of the magnetic sensor 10 and the like.

Next, the configuration of the circuits of the magnetic sensor 10 will be described with reference to FIG. The constant current circuit 22 supplies a constant current to the input terminal of the semiconductor Hall element 17. The constant current circuit 22 is connected to a power supply + Vcc via a variable resistor R1 so that the magnitude of the constant current can be adjusted by the variable resistor R1. The output terminal of the semiconductor Hall element 17 is connected to the zero point temperature compensation circuit 23.

The zero point temperature compensating circuit 23 corresponds to FIGS.
As described above, the voltage −V _Z (T) having the opposite sign and the same absolute value as the temperature drift V _Z (T) at the zero point of the output voltage of the semiconductor Hall element 17 is applied to the semiconductor Hall element 17.
This is a circuit for adding to the output voltage V _OUT (T). −V _Z
The voltage corresponding to (T) is generated in the buffer circuit 24 according to the ambient temperature of the semiconductor Hall element 17 detected by the temperature sensor 18 and supplied to the zero point temperature compensation circuit 23 via the variable resistor R2. .

In the present embodiment, as shown in FIG.
By using the semiconductor Hall element 17 made of gallium arsenide, the zero point compensation voltage −V _Z (T) changes substantially linearly in accordance with a temperature change, so that the buffer circuit 24 generates −V _Z (T). Can be done easily. Note that the variable resistor R
2 has a role of adjusting the slope of −V _Z (T) as necessary.

The output terminal of the zero point temperature compensation circuit 23 is connected to a zero point adjustment circuit 25, and the zero point temperature compensation circuit 23 is connected to a power supply + Vcc via a variable resistor R3. Point adjustment is performed. Specifically, the output voltage of the semiconductor Hall element 17 temperature-compensated by the zero-point temperature compensation circuit 23 increases as the distance between the semiconductor Hall element 17 and the proximity object 15 decreases. For convenience of measurement, the output voltage is converted so as to decrease as the distance from the proximity object 15 decreases.

In the zero point adjusting circuit 25, the bottom dead center of the stroke of the press machine 13 (for example, the distance between the proximity body 15 and 1000 μm) is set to the zero point. The output voltage of the adjustment circuit 25 is adjusted by the variable resistor R3 so as to be 0 [V].
Note that the output of the zero point adjustment circuit 25 is input to the amplification circuit 26, and after the amplification (span adjustment) is performed at a desired amplification rate by the amplification circuit 26, the output of the amplification circuit 26 is changed to the output of the magnetic sensor 10 Is done. Among the circuits of the magnetic sensor 10, the semiconductor Hall element 17 and the temperature sensor 18 are arranged on the printed circuit board 16, but the other constant current circuit 22, power supply + Vcc, etc.
The printed circuit board 16 is connected to a printed circuit board 16 by a lead wire or the like. However, the constant current circuit 22 and the power supply + Vcc are also used for the magnetic sensor 1.
It is also possible to dispose it on the printed circuit board 16 of the main body.

Hereinafter, an output example of each part of the circuit of FIG. 12 will be described. The output voltage of the semiconductor Hall element 17 is, for example, as shown in Table 1 and FIG. As is clear from FIG. 6, even when the distance between the magnetic sensor 10 and the proximity body 15 is the same, the output voltage decreases as the ambient temperature of the semiconductor Hall element 17 increases.

Next, the output voltage of FIG. 6 is input to the zero point temperature compensation circuit 23, and the output after the zero point temperature compensation circuit 23 performs temperature compensation is as shown in Table 3 and FIG. The zero point temperature compensation circuit 23 compensates so that the output voltage at the stroke bottom dead center of the press machine 13, that is, when the distance between the magnetic sensor 10 and the proximity body 15 is 1000 μm, is substantially constant regardless of the temperature. It is carried out. Referring to FIG. 13, even at points other than the bottom dead center of the stroke, the six curves substantially overlap, and the temperature compensation is suitably performed.

[0045]

[Table 3]

Next, the output of the zero point temperature compensating circuit 23 shown in FIG.
Table 4 and FIG. 14 show the output after the zero point was adjusted in Step 5. As is apparent from FIG. 14, the output voltage of the zero point adjustment circuit 25 is converted so as to decrease as the distance decreases, and the output voltage of the zero point adjustment circuit 25 at a stroke bottom dead center of a distance of 1000 μm. Is set to be approximately 0 [V] regardless of the temperature. In addition, the six curves for each temperature substantially overlap at points other than the stroke bottom dead center, and the temperature drift is suitably compensated.

[0047]

[Table 4]

Next, the output of the zero point adjustment circuit 25 shown in FIG. 14 is input to the amplification circuit 26, and the output of the amplification circuit 26 after amplification at a predetermined amplification factor is shown in Table 5 and FIG. FIG.
As is clear from FIG. 5, the sensor output after amplification is
Approximately 0 regardless of temperature at the bottom dead center of a stroke of 000 μm
[V], and the six curves for each temperature substantially overlap other than the bottom dead center of the stroke.

From the above experimental results, in the magnetic sensor 10 of the present embodiment, the temperature range is 0 ° C. to 50 ° C., and the distance between the magnetic sensor 10 and the proximity body 15 is 500 to 15 ° C.
It was proved that measurement was possible with a high accuracy of ± 1 μm in the range of 00 μm (measurement range 1 mm). The press 13
In the case of monitoring the bottom dead center, in the above-described measurement range of 500 to 1500 μm, substantially 1000 to 1500 μm
, But depending on the application, the entire measurement range of 500 to 1500 μm can be used.

[0050]

[Table 5]

When the magnetic sensor 10 is used for monitoring the bottom dead center of the stroke of the press machine 13, the distance can be measured with extremely high accuracy. The distance between the magnetic sensor 10 and the proximity body 15 at the stroke bottom dead center at each press is not a previous value comparison comparing the bottom dead center position at the time of this press but a predetermined value (for example, 1000 μm). ) Can be determined by comparing the absolute values. Therefore,
The magnetic sensor 10 includes, for example, an upper mold 11 or a lower mold 12.
Even if the position of the bottom dead center of the stroke is shifted up or down by about 1 μm due to the entry of foreign matter into the
Defective products can be detected reliably and with high accuracy.

In the above embodiment, the case where the magnetic sensor 10 is attached to the side surface of the lower mold 12 has been described.
For example, the magnetic sensor 10 may be provided near the upper end of the lower mold 12 in an embedded form, and directly measure the distance between the magnetic sensor 10 and the upper mold 11 made of a magnetic material. Even in this case, since the magnetic sensor 10 performs magnetic shielding with the outer case 21 made of a non-magnetic material, even if the lower mold 12 is a magnetic material,
No decrease in measurement accuracy occurs.

Further, in the above-described embodiment, an example in which the magnetic sensor 10 is used for monitoring the bottom dead center of the press machine 13 has been described. However, the magnetic sensor 10 may be, for example, beside a gear made of a magnetic material. The present invention can be used for various applications involving measurement of a distance to a target made of a magnetic material, such as measurement of runout, distortion, parallelism, surface deflection of a magnetic drum, and parallelism. It should be noted that by using a magnet that generates a magnetic field of 3000 Gauss or more as the magnet 19, it is possible to measure with high accuracy of about ± 1 μm. As 19, a member that generates a magnetic field of less than 3000 Gauss can also be used.

When the semiconductor Hall element 17 is made of a semiconductor such as gallium arsenide having a substantially linear temperature characteristic at the zero point, there is an advantage that the temperature compensation at the zero point can be performed with high accuracy.
Even when the semiconductor Hall element 17 is made of a semiconductor whose temperature characteristics are non-linear such as silicon and indium antimony, the absolute value of the sensitivity temperature coefficient of the semiconductor Hall element 17 and the absolute value of the resistance temperature coefficient of the input resistance are made substantially the same. As a result, the sensitivity temperature characteristic and the resistance temperature characteristic can be canceled and compensated for each other with high precision, and the point that only the temperature compensation of the zero point needs to be performed remains unchanged, so that the sensor can be practically used as a proximity distance sensor.

[0055]

According to a first aspect of the present invention, there is provided a magnetic sensor for measuring a distance between a magnetic substance and an object, comprising: a substrate; a semiconductor Hall element disposed on a surface of the substrate; A magnet arranged on the back side of the substrate to generate a magnetic field penetrating the semiconductor Hall element, a constant current circuit for supplying a constant current to the semiconductor Hall element, a temperature sensor arranged on the substrate, A zero-point temperature compensation circuit for compensating a temperature characteristic of a zero point of the semiconductor Hall element according to a temperature detected by a sensor, wherein a sensitivity temperature coefficient of the semiconductor Hall element and a resistance of an input resistance of the semiconductor Hall element are provided. Since the temperature coefficient is set so that the positive and negative signs are opposite to each other and the absolute values are substantially equal,
The sensitivity temperature characteristic of the semiconductor Hall element is canceled and compensated with high accuracy by the resistance temperature characteristic of the input resistance, and the output voltage of the semiconductor Hall element hardly fluctuates depending on the sensitivity temperature characteristic and the resistance temperature characteristic. Therefore, in the present invention,
As for the temperature compensation, it is only necessary to compensate the temperature characteristic of the zero point by the above-mentioned zero point temperature compensation circuit, so that the temperature compensation becomes easy. Even when used for measurement, sufficient measurement accuracy (for example, about ± 1 μm) can be obtained.

In the magnetic sensor according to the second and third aspects, the semiconductor Hall element is formed of a semiconductor whose temperature characteristic at the zero point is substantially linear, for example, gallium arsenide. It can be performed extremely easily and with high accuracy, and therefore, the measurement accuracy by the present magnetic sensor can be further improved.

In the magnetic sensor according to the fourth aspect of the present invention, since the inner case made of a magnetic material is provided so as to cover the periphery of the magnet, magnetic lines of force extending from the magnet to the inner case through the semiconductor Hall element are formed. Therefore, directivity is given to the magnetic field of the magnet by the inner case, and a larger magnetic field penetrates the semiconductor Hall element than when the inner case is not provided. As a result, the semiconductor Hall element has a small magnetic field. Can be detected, so that the measurement accuracy of the magnetic sensor can be further improved.

In the magnetic sensor according to the fifth aspect, since the outer case made of a non-magnetic material is provided so as to cover the periphery of the inner case, a case where the present magnetic sensor is attached to another magnetic material is provided. However, it is possible to prevent the problem that the magnetic sensor is magnetically shielded by the outer case and the measurement accuracy of the present magnetic sensor is reduced by the presence of another magnetic substance.

In the magnetic sensor according to claims 6 and 7, since the magnet is a magnet capable of generating a magnetic field having a magnetic flux density of 3000 gauss or more, for example, a neodymium-based rare earth magnet, The penetrating magnetic field becomes sufficiently large, and the semiconductor Hall element can detect even a very small change in the magnetic field.
Measurement accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an ambient temperature of a semiconductor Hall element and sensitivity.

FIG. 2 is a graph showing a relationship between an ambient temperature of a semiconductor Hall element and an input resistance.

FIG. 3 is an explanatory diagram showing a schematic configuration of a magnetic sensor of the present invention.

FIG. 4 is a graph showing how the output of a semiconductor Hall element fluctuates due to temperature characteristics at a zero point.

FIG. 5 is a graph showing a compensation voltage for compensating the temperature characteristic at the zero point.

FIG. 6 is a graph showing a relationship between a distance between a Hall element made of gallium arsenide and an object (magnetic material) and an output at a plurality of temperatures.

FIG. 7 is a graph showing the relationship between the temperature and the output of the Hall element when the distance is constant.

FIG. 8 is a graph showing a relationship between a distance between a Hall element made of indium antimony and an object (magnetic material) and an output at a plurality of temperatures.

FIG. 9 is a schematic front view showing a press equipped with a magnetic sensor according to the embodiment of the present invention.

FIG. 10 is a schematic plan view showing a lower die in the press machine.

FIG. 11 is an explanatory sectional view showing the magnetic sensor.

FIG. 12 is a block diagram showing a configuration of circuits in the magnetic sensor.

FIG. 13 is a graph showing the output of a zero point temperature compensation circuit in the magnetic sensor for a plurality of temperatures.

FIG. 14 is a graph showing the output of a zero point adjustment circuit in the magnetic sensor at a plurality of temperatures.

FIG. 15 is a graph showing the output of an amplifier circuit in the magnetic sensor at a plurality of temperatures.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magnetic sensor 15 Neighbor (object) 16 Printed circuit board (substrate) 17 Semiconductor Hall element 18 Temperature sensor 19 Magnet 20 Inner case 21 Outer case 22 Constant current circuit 23 Zero point temperature compensation circuit

Continuing from the front page (72) Inventor Koji Ota 49-1, Abe, Oji, Sakurai-shi, Nara F-term in RIKEN Keiki Nara Works (reference) 2F063 AA02 BA21 BD15 CB01 CB05 GA53 GA55 JA09 LA11 LA22 LA30 2G017 AA02 AA05 AA06 AB05 AB07 AB08 AC01 AC04 AC06 AC07 AD53 AD59

Claims (7)

[Claims] 1. A magnetic sensor for measuring a distance between a magnetic body and an object, comprising: a substrate; a semiconductor Hall element disposed on a surface of the substrate;
A magnet arranged on the back side of the substrate for generating a magnetic field penetrating the semiconductor Hall element, a constant current circuit for supplying a constant current to the semiconductor Hall element, a temperature sensor arranged on the substrate, and the temperature sensor A zero-point temperature compensating circuit for compensating for the temperature characteristic of the zero point of the semiconductor Hall element according to the temperature detected in the above step, wherein the sensitivity temperature coefficient of the semiconductor Hall element and the resistance temperature of the input resistance of the semiconductor Hall element A coefficient is set so that the positive and negative signs are opposite to each other and their absolute values are substantially equal. 2. The magnetic sensor according to claim 1, wherein the semiconductor Hall element is formed of a semiconductor having a substantially linear temperature characteristic at a zero point. 3. The magnetic sensor according to claim 2, wherein said semiconductor is gallium arsenide. 4. An inner case made of a magnetic material is provided so as to cover the periphery of the magnet, whereby magnetic lines of force extending from the magnet through the semiconductor Hall element to the inner case are formed. Item 4. The magnetic sensor according to any one of Items 1 to 3. 5. The magnetic sensor according to claim 4, wherein an outer case made of a non-magnetic material is provided so as to cover a periphery of the inner case. 6. The magnet according to claim 1, wherein said magnet generates a magnetic field having a magnetic flux density of 3000 gauss or more.
The magnetic sensor according to any one of the above. 7. The magnetic sensor according to claim 6, wherein the magnet is a neodymium rare earth magnet.