JPH08241806A - Non-contact position sensor - Google Patents

Abstract

PURPOSE: To provide a non-contact position sensor which is equipped with a semiconductor magnetoresistor and restrained from varying in output characteristics due to a temperature change without using a temperature compensating circuit. CONSTITUTION: A non-contact position sensor is basically composed of two semiconductor magnetoresistors (magnetoresistive devices) 8 which are electrically connected together in series and a magnet 5 which is arranged at a position confronting the magnetoresistive device 8 and whose surface confronting the magnetoresistive device 8 is displaced in phase attendant on the pivoting of a rotary shaft 3. A prescribed voltage is applied to the one of the semiconductor magnetoresistors (magnetoresistive device) 8, and the other is grounded. The partial potential obtained from the junction of the semiconductor magnetoresistors 8 is taken out as the displacement data of the rotary shaft on the basis of the resistances of the magnetoresistors which are changed in resistance corresponding to a magnetic field strength which varies in accordance with a relative positional relation to the magnet 5. In this case, a bias magnet 6 is provided at a position confronting the magnet 5 through the intermediary of the magnetoresistive device 8 so as to give a prescribed offset magnetic field corresponding to a change point of a magnetic field strength - resistance characteristics to the magnetoresistive device 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type position sensor for detecting a rotational position, a moving position and the like of an object to be detected in a non-contact manner, and more particularly to two semiconductor magnetic resistors electrically connected in series. The present invention relates to the realization of a sensor structure for suppressing the output fluctuation due to the temperature of the same sensor that detects the position of a detected object using.

[0002]

2. Description of the Related Art Conventionally, for example, a rotary position sensor used as a throttle opening sensor of an in-vehicle internal combustion engine, a linear position sensor used as a valve stroke sensor of the engine, or the like is used to detect a rotation angle or a linear movement amount of an object to be detected. Sliding resistors were often used as the detecting sensor.

However, this sliding resistor has many problems in terms of accuracy as those sensors, such as fluctuations in its output characteristics and noise due to wear and stain on the sliding portion. It was

Therefore, in recent years, for example, Japanese Examined Patent Publication No. 63-664.
As in the position sensor described in Japanese Patent Laid-Open No. 04-04, a so-called non-contact type that detects the rotation angle and the linear movement amount of the detected object in a non-contact manner by using two magnetic resistors (elements) that are electrically connected in series Contact type position sensors have come into use.

Incidentally, in such a non-contact type position sensor,
A magnet disposed at a position facing the surface on which the magnetic resistor is disposed changes as a resistance value change of the magnetic resistor corresponding to a change in magnetic field strength when the magnet is displaced due to rotation or movement of the object to be detected. The position of the detector is detected. For this reason,
Since the sensor element itself does not have a sliding portion, there is no concern that output characteristics will change or noise will be generated due to wear or stain.

However, even in the non-contact type position sensor using this magnetic resistor, it is unavoidable that the output changes due to the temperature change in the surroundings. Therefore, even if the detected object is rotated by the same angle or moved by the same amount. However, different position information is output when the temperature is high and when the temperature is low.

Then, recently, further, for example, JP-A-48-4
Like the position sensor disclosed in Japanese Patent No. 8087, the temperature compensation is performed by connecting one to a plurality of diodes in series or in parallel with the magnetic resistor (element). Alternatively,
As in the position sensor disclosed in Japanese Patent Publication No. 3-58446: -Thermistor is used to perform temperature compensation of the magnetoresistive element (element). Non-contact position sensors having various temperature compensation circuits have been proposed.

[0008]

According to the non-contact type position sensor having such a temperature compensating circuit, it is possible to surely suppress the output fluctuation due to the temperature change as the sensor.

However, in these conventional non-contact type position sensors, the increase in cost and size due to the addition of the temperature compensating circuit cannot be avoided, and the temperature compensating effect itself is, for example, the above-mentioned throttle opening sensor. It was still insufficient for precise measurement applications such as or as a valve stroke sensor.

The present invention has been made in view of the above circumstances, and it is possible to use the above temperature compensating circuit and the like,
An object of the present invention is to provide a non-contact type position sensor capable of suitably suppressing a change in output characteristic due to a temperature change.

[0011]

In order to achieve such an object, in the invention according to claim 1, two semiconductor magnetic resistors electrically connected in series and a surface on which the magnetic resistors are disposed are opposed to each other. Displacement transmission means for relatively displacing the phase of the magnet means arranged at the position and the facing surfaces of the magnetoresistive body and the magnet means in the connecting direction of the two magnetoresistive bodies as the detected body is displaced. A power supply means for grounding one end of the series-connected magnetic resistors and applying a predetermined voltage to the other end, and a magnetic field based on the relative positional relationship between the supplied magnetic resistors and the magnet means. Output means for taking out a partial pressure value from the connection point as displacement information of the detected body based on the resistance value of each of the magnetic resistors that changes according to the strength, and at least in a state where the detected body is displaced. The two magnetic resistors Body mutually field strength - comprises a magnetic circuit for operating in a different magnetic flux density regions of the resistance value characteristic constitutes a non-contact type position sensor.

According to the invention described in claim 2,
In the configuration of the invention described above, the magnetic circuit, a bias for applying a predetermined offset magnetic field corresponding to the magnetic field strength of the point where the magnetic field strength-resistance value characteristics of the magnetic resistance itself changes to the magnetic resistance. It is configured to include a means.

According to the invention described in claim 3,
In the configuration of the invention described above, the bias means is constituted by a bias magnet arranged at a position facing the magnet means via the magnetic resistor.

According to a fourth aspect of the invention, in the configuration of the second aspect of the invention, the bias means is integrated with the magnet means in order to increase the facing area of the magnet means with the magnetic resistor. It is composed of a magnetic substance added to.

According to a fifth aspect of the invention, in the configuration of the second aspect of the invention, the bias means is arranged to increase the area of the magnetic field emitted from the magnet means to the magnetic resistor. It is composed of a magnetic body interposed between the magnet means and the magnetic resistor.

According to the sixth aspect of the present invention, two semiconductor magnetic resistors electrically connected in series, magnet means arranged at a position facing the surface where the magnetic resistors are arranged, and the detected object are detected. Displacement transmitting means for relatively displacing the phase of the facing surfaces of the magnetic resistor and the magnet means in the connecting direction of the two magnetic resistors according to the displacement of the body, and the magnetic resistor connected in series. Feeding means for grounding one end and applying a predetermined voltage to the other end, and each of the magnetic resistors that changes according to the magnetic field strength due to the relative positional relationship between the fed magnetic resistor and the magnet means. In the non-contact type position sensor, the partial pressure value from the connection point is taken out as displacement information of the object to be detected based on the resistance value of Different magnetic resistors That the magnetic field strength - a configuration that uses a magnetoresistive element operating at the resistance value properties as the semiconductor magnetoresistive element.

Further, in the invention according to claim 7, two semiconductor magnetic resistors electrically connected in series, magnet means arranged at a position opposed to an arrangement surface of the magnetic resistors, and a detected object are detected. Displacement transmitting means for relatively displacing the phase of the facing surfaces of the magnetic resistor and the magnet means in the connecting direction of the two magnetic resistors according to the displacement of the body, and the magnetic resistor connected in series. Feeding means for grounding one end and applying a predetermined voltage to the other end, and each of the magnetic resistors that changes according to the magnetic field strength due to the relative positional relationship between the fed magnetic resistor and the magnet means. In the non-contact type position sensor having an output means for taking out a partial pressure value from the connection point as displacement information of the detected object on the basis of the resistance value of, the magnet means is displaced by at least the detected object. In the state where Field strength One of the magnetoresistive element to one another -
The magnetic force is set so that it can be operated in the magnetic flux density regions having different resistance characteristics.

[0018]

In the structure of the invention described in claim 1, the two semiconductor magnetic resistors, the magnet means, the displacement transmitting means, the power feeding means, and the output means constitute a normal basic non-contact type position sensor. In such a position sensor, the output characteristics fluctuate due to changes in the surrounding temperature, and even when the detected object rotates at the same angle or moves by the same amount, different position information is obtained at high temperature and at low temperature. Is output as described above. This will be described in more detail.

The magnetic field strength (B) -resistance value (R) characteristic of the semiconductor magnetic resistor (element) is R = (1 + μ ^ (2) B ^ (2)) Ro in a low magnetic field. (A), and in a high magnetic field, it is approximated as R = (a + b μB) Ro (b). Here, Ro is the resistance value of the same semiconductor magnetoresistor when the magnetic field is “0”, μ is the electron mobility in the semiconductor, and a and b are the proportional constants peculiar to the magnetoresistor. Also, in the above formula (a), "^"
Represents power, and “^ (2)” means “square”.

As described above, the semiconductor magnetoresistive element itself has its resistance value changed according to the magnetic field strength in accordance with the square characteristic of the above equation (a) in a low magnetic field, and in a high magnetic field. The resistance value changes according to the magnetic field strength according to the first-order characteristic of the equation (b).

However, in the conventional position sensor, the magnetic field strength applied to the magnetoresistive body by the magnet means is usually small in the first place, so that the magnet means and the magnetoresistive body are displaced by the displacement of the object to be detected. No matter which phase is used, the magnetoresistive element itself is
The resistance value changes according to the squared characteristic.

Therefore, in this case, as will be described later in detail in the embodiment, when the displacement of the object to be detected is other than "0",
That is, the magnetic field strength B applied to the two magnetoresistive bodies
, The magnetic resistances have different temperature fluctuations that cannot be canceled out, and the resistance ratios of the magnetic resistances do not correspond purely to the displacement of the detected object. .

On the other hand, due to these characteristics of the semiconductor magnetoresistive element, when the two magnetoresistive elements are placed in a predetermined high magnetic field, the magnetic resistive element close to the magnet means is in a high magnetic field. The resistance value changes according to the first-order characteristic of the formula (b), and the magnetic resistor on the side separated from the other magnet means is in a low magnetic field,
The resistance value changes according to the squared characteristic of the equation. When the two magnetoresistive elements simultaneously operate according to different characteristics as described above, the temperature dependency of each of the magnetoresistive elements becomes different, as will be described later in detail in the embodiment. The variation in the resistance ratio (output) of the magnetic resistors can be suppressed.

Therefore, according to the first aspect of the present invention, the two magnetic resistors are operated in the magnetic flux density regions having different magnetic field strength-resistance value characteristics at least in the state where the object to be detected is displaced. Magnetic circuit to make. With such a configuration, the semiconductor magnetoresistive body satisfies these conditions, and it is possible to suppress the change in the output characteristic due to the temperature change without providing any special temperature compensation circuit. Become.

Further, according to the invention of claim 2,
The magnetic circuit includes: a bias means for applying a predetermined offset magnetic field corresponding to the magnetic field strength at the point where the magnetic field strength-resistance value characteristic of the magnetic resistance itself changes to the magnetic circuit. With this configuration, when the object to be detected is displaced, the two magnetic resistors can be reliably operated in the magnetic flux density regions having different magnetic field strength-resistance value characteristics. That is, the above condition for suppressing the temperature fluctuation is surely satisfied.

Incidentally, the square characteristic of the above equation (A) has a characteristic such as R = 7.816 × 10 ^ (4) × B ^ (2) + 1150Ω, and the square characteristic of the above equation (B) is as follows: In the case of a semiconductor magnetoresistor having characteristics such as R = 1.49 × 10 ^ (4) × B + 827Ω, it was confirmed that the magnetic field strength at the point where the above characteristics change is “0.166T (Tesla)”. ing.

As the bias means, for example, as in the invention according to claim 3, a bias magnet arranged at a position facing the magnet means via the magnetic resistor is used. Alternatively, as in the invention according to claim 4, a structure is used in which a magnetic body is integrally added to the magnet means in order to increase the facing area of the magnet means with the magnetic resistor. Furthermore, according to the invention of claim 5, the magnetic field interposed between the magnet means and the magnetoresistive body in order to increase the area of the magnetic field emitted from the magnet means to the magnetoresistive body. Configuration using the body. And so on. Particularly, according to the configuration of the invention of claim 3 which uses the bias magnet, it is relatively easy to
Moreover, it becomes possible to accurately apply a predetermined offset magnetic field to the magnetoresistive body. Further, according to the structure of the invention of claim 4 or 5, which expands the function as the magnet means, the temperature compensation equivalent to the above is realized in a more compact form which does not require the arrangement of the bias magnet. A non-contact type position sensor having a function can be configured.

By the way, the above condition for suppressing the temperature fluctuation is not always achieved only by the magnetic circuit. That is, as the characteristics of the semiconductor magnetic resistor itself, if the magnetic field strength at the point where the characteristics change is small, that is, at a smaller magnetic field strength, there is a magnetic field strength-resistance value characteristic in which the squared characteristic and the squared characteristic intersect. If it is a semiconductor magnetic resistor, the same condition that the two magnetic resistors simultaneously operate according to different characteristics is satisfied without providing the magnetic circuit.

Therefore, in the invention of claim 6, in the structure of the basic non-contact type position sensor, at least when the object to be detected is displaced, the two magnetic resistors have different magnetic field strength-resistance. A magnetoresistive element that operates with a value characteristic is used as the semiconductor magnetoresistive element.

With such a structure, the semiconductor magnetic resistor can also satisfy the above condition, and it is possible to suppress the change of the output characteristic due to the temperature change without providing any special temperature compensating circuit. .

The same condition for suppressing the temperature fluctuation can be satisfied by setting the magnetic force in the magnet means without separately providing the magnetic circuit. That is, as in the invention according to claim 7, in the same basic configuration of the non-contact type position sensor, the magnet means includes the two magnetic resistance bodies at least in a state in which the detected body is displaced. It is set to a magnetic force capable of operating in magnetic flux density regions having different magnetic field strength-resistance value characteristics. By adopting such a configuration, the same condition can be satisfied in the semiconductor magnetoresistive body, and it becomes possible to suppress the fluctuation of the output characteristic due to the temperature change without providing any special temperature compensation circuit. .

[0032]

FIG. 1 shows an embodiment of a non-contact type position sensor according to the present invention. The position sensor of this embodiment is configured as the above-described rotary position sensor, for example, as a position sensor that detects a rotation angle (displacement) of a detected object such as a throttle opening of an on-vehicle internal combustion engine in a non-contact manner.

First, a sensor structure as a non-contact type position sensor according to this embodiment will be described with reference to FIG. In the position sensor of this embodiment shown in FIG. 1, the housing 1 is a part that integrally holds and protects the following components that form the position sensor. A rotary shaft 3 as an object to be detected is rotatably supported by the housing 1 via a bearing 2.

A holder 4 is attached to the rotary shaft 3 at the end thereof inside the housing 1. A magnet (permanent magnet) 5 is attached to the bottom of the holder 4 at a position offset from the center of rotation of the rotary shaft 3.

On the other hand, on the inner bottom surface of the housing 1,
A bias magnet (permanent magnet) 6 is provided. Then, on the upper surface of the bias magnet 6, a magnetoresistive element 8 in which a semiconductor magnetoresistive body is formed on an insulating substrate is arranged via a yoke 7 made of soft iron as a magnetic collector. The surface of the magnetoresistive element 8 on which the semiconductor magnetoresistive element is formed and the magnet 5
The dimensions of each of the above component elements are determined so as to face the bottom surface of the component element with a predetermined gap.

The magnetoresistive element 8 has two semiconductor magnetoresistive elements electrically connected in series, as will be described later. The electrodes corresponding to both ends and connection points of the magnetic resistors are connected to the power supply terminal 10 and the ground terminal 1 which are led out from the bottom of the housing 1.
1 and the output terminal 12 are electrically connected to each other via lead wires 9.

FIG. 2 shows, for reference, the sectional structure of the position sensor of this embodiment when it is cut horizontally from the magnet 5 portion. With such a structure as the same position sensor, the magnet 5 moves along with the rotation of the rotary shaft 3 that is the detected object.
In the mode shown by the arrow in FIG. 2, that is, the phase of the surface facing the magnetoresistive element 8 is displaced, so that the magnetoresistive element 8 is rotated on the same.

On the other hand, in the magnetoresistive element 8, the above two magnetoresistive bodies receive the magnetic fields having the strengths corresponding to the phase relationship with the magnet 5, and the two magnetic resistances are received in accordance with the received magnetic field strengths. The resistance value of the body changes.

Further, particularly in the position sensor of the embodiment, the bias magnet 6 is arranged so that a predetermined offset magnetic field is applied to the magnetoresistive element 8. FIG. 3 shows an equivalent circuit of the position sensor of the embodiment having such a configuration.

As shown in FIG. 3 and as described above, the magnetoresistive element 8 has two magnetoresistive elements electrically connected in series. Then, the power supply voltage Vcc is applied to the power supply terminal 10 to which one ends of the magnetic resistors are connected, and the other end is grounded via the ground terminal 11.

Further, the magnet 5 is equivalent to the magnetoresistive element 8 in a mode shown by an arrow in FIG.
The bias magnet 6 is displaced along with the rotation of the object to be detected (rotary shaft 3), and applies an offset magnetic field to the magnetoresistive element 8 in the manner shown in FIG.

The output terminal 12 as the same position sensor is led out from the connection point of the two magnetic resistors connected in series. From the output terminal 12, the resistance ratio of each of the magnetic resistors, which changes in accordance with the magnetic field strength due to the relative positional relationship between the magnetoresistive element 8 and the magnet 5, is, to be exact, a divided voltage value by the resistance ratio. Vo is output as displacement information (rotation angle information of the rotation shaft 3) of the detected object.

Assuming that the resistance values of the two magnetic resistors are R1 and R2, respectively, as shown in FIG. 3, this displacement information (divided voltage value) Vo is Vo = Vcc × R2 / (R1 + R2 ) ... (1).

Next, how the position sensor of this embodiment performs temperature compensation will be described based on the results of experiments. In the configuration of the position sensor of the embodiment, the output variation Δθ with respect to the temperature of the position sensor was measured while variously changing the strength of the offset magnetic field applied by the bias magnet 6, and the result shown in FIG. 5 was obtained. It was

First, FIG. 5A shows the output (displacement information (partial pressure value) Vo) when the rotary shaft 3 which is the object to be detected is at a position of 50 ° (FS: full scale). Shows the temperature fluctuation of.

At this position, when the applied offset magnetic field B is "0", that is, when the condition is the same as that of the conventional position sensor without the bias magnet 6, FIG.
As shown by the characteristic line PA in (a), an extremely large output fluctuation occurs. From "-30 ° C" to "+
Output fluctuation range due to changes in ambient temperature up to 120 ° C
The angle converted value was “32 °”.

On the other hand, the object to be detected (rotary shaft 3) is at the same 50 °
When an offset magnetic field was applied by the bias magnet 6 at the (FS) position, the output fluctuation range decreased as the magnetic field strength increased. And "0.183T"
When the offset magnetic field of 1 is given, the output fluctuation range is "1" as shown by the characteristic line D1 in FIG.
It was reduced to "°".

Further, by further increasing the magnetic field strength of such an offset magnetic field, for example, the characteristic line D3 or D in FIG.
As shown by 4, when the offset magnetic field of “0.223T” or “0.369T” is applied, the output fluctuation Δθ exhibits a positive temperature dependence. The output fluctuation range increased as the intensity increased.

On the other hand, FIG. 5B shows the temperature fluctuation of the output when the object to be detected (rotating shaft 3) is at the position of 0 °, and FIG. 5C shows the object to be detected (rotating shaft 3). ) Is -25 ° (-
F. S. The temperature fluctuation of the output at the position of / 2) is shown respectively.

Even at these positions, when the applied offset magnetic field B is "0" (in the case of the conventional position sensor), as indicated by characteristic lines PA, respectively,
Although some output fluctuations have occurred, when the above-mentioned "0.183T" offset magnetic field is applied, each characteristic line D
As shown by 1, the output fluctuation range is still “1 °”
It was reduced to the extent.

The reason why the temperature variation of the output is suppressed by applying the appropriate offset magnetic field in this way is as follows.
It is considered as follows. (Characteristics of Semiconductor Magnetic Resistor) First, the characteristics of the semiconductor magnetic resistor itself will be considered.

In the semiconductor magnetic resistor, if the magnetic flux density is B and the resistance value of the magnetic resistor when the magnetic field of the magnetic flux density B is applied is R (B), the resistance value R (B )
Is approximated as R (B) = (1 + μ ^ (2) B ^ (2)) Ro ... (2) in low magnetic fields, and R (B) = (a + bμB) Ro ... (3) in high magnetic fields. Is approximated as. In these equations, Ro is the resistance value of the same semiconductor magnetoresistive element when the magnetic field is “0”, μ is the electron mobility in the semiconductor, and a and b are the proportional constants peculiar to the magnetoresistive element. is there. In the above equation (2), "^" means exponentiation and "^ (2)" means "squared".

As described above, the semiconductor magnetoresistive element itself changes its resistance value in accordance with the magnetic field strength in accordance with the square characteristic (quadratic function of μB) of the above equation (2) in a low magnetic field.
Further, in a high magnetic field, the first-order characteristic (μB
The resistance value changes according to the magnetic field strength.

Here, assuming that the mobility μ is mainly governed by lattice scattering, the mobility μ becomes proportional to the absolute temperature (T) raised to the (−3/2) th power. It can be expressed as μ = cT ^ (-3/2) (4).

Therefore, this equation (4) is converted into the above (2).
Substituting into equation (3) and equation (3) respectively, the above resistance value R
(B) becomes R (B) = (1 + c ^ (2) T ^ (-3) B ^ (2)) Ro ... (5) in the low magnetic field, and R (B) = (in the high magnetic field. a + bcT ^ (-3/2) B) Ro (6)

FIG. 4 shows the magnetic field strength-resistance value characteristics of such a semiconductor magnetic resistor. This FIG. 4 shows a magnetoresistive element 8
InSb is used as the semiconductor magnetoresistor formed in
6 is a graph showing the results of measuring the magnetic field strength-resistance value characteristics at an ambient temperature of 25 ° C. (298K). In addition, in FIG. 4, the above formula (2) or (5) is used.
The characteristic line relating to the characteristic of the formula is set as the line SL, and the characteristic line relating to the characteristic of the formula (3) or (6) is defined as the line SH.
Are respectively shown as. When the values of these characteristic lines SL and SH are obtained from the measurement results of FIG. 4,
The characteristic line SL is R (B) = 7.816 × 10 ^ (4) × B ^ (2) +1150 [Ω], and the characteristic line SH is R (B) = 1.49 × 10. ^ (4) x B + 827 [Ω].

The intersection of these characteristic lines SL and SH,
That is, the change in the resistance value of the semiconductor magnetoresistive element is (2) above.
The change point at which the characteristic of equation (5) is switched to the characteristic of equation (3) or equation (6) is about "0.166".
It is clear from FIG. 4 that this corresponds to the magnetic field strength of “T (Tesla)”. Incidentally, the resistance value of the semiconductor magnetic resistor at that time is about “3.3 kΩ (kilo ohm)”.

According to the characteristic lines SL and SH, the above constants of the semiconductor magnetoresistive element used in the experiment are Ro = 1150 [Ω] a = 0.719 b = 1.58 c = 4.24, respectively. It is estimated to be × 10 ^ (4) [K ^ (3/2) T ^ (-1)].

(Temperature Characteristic of Conventional Position Sensor) Next, the temperature characteristic of the conventional position sensor without the bias magnet 6 will be considered.

In such a conventional position sensor, since the magnetic field strength applied to the semiconductor magnetoresistive element is small in the first place, the resistance values R1 and R2 of these magnetoresistive elements are both quadratic functions of the above μB, and the above (5) It becomes to be expressed by the relation of formula. That is, assuming that the magnetic field strengths applied to the magnetoresistive body are B1 and B2, respectively, R1 = (1 + c ^ (2) T ^ (-3) B1 ^ (2)) Ro (7) R2 = (1 + c ^ (2 ) T ^ (-3) B2 ^ (2)) Ro (8).

The output Vo of the same position sensor at this time
Is obtained by substituting these equations (7) and (8) into the above equation (1), Vo = Vcc {1 + c ^ (2) T ^ (-3) B2 ^ (2)} / {2 + c ^ (2) T ^ (-3) (B1 ^ (2) + B2 ^ (2))} (9).

On the other hand, the temperature dependence of the output Vo is obtained by differentiating the equation (9) by the absolute temperature T, and dVo / dT = 3Vcc · c ^ (2) T ^ (-4) (B1 ^ (2) -B2 ^ (2)) / {2 + c ^ (2) T ^ (-3) (B1 ^ (2) + B2 ^ (2))} ^ (2) ... (10).

Here, from the equation (10), the temperature dependence of the detected body (rotating shaft 3) is set to θ, and the temperature dependence is verified as follows: (1) If θ <0, B1> B2 Therefore, dV
o / dT> 0 (2) When θ = 0, B1 = B2, so dV
When o / dT = 0 (3) θ> 0, B1 <B2, and therefore dV
o / dT <0.

That is, in this conventional position sensor, when θ ≠ 0 (B1 ≠ B2), dVo / dT is always satisfied.
≠ 0, and it can be seen that the fluctuation of the output Vo due to the temperature is unavoidable.

In the position sensor used in the above experiment, the object to be detected is θ = F. S. Since B1 and B2 at the position of (50 °) are B1 = 0.025 [T] and B2 = 0.141 [T], respectively, the power supply voltage Vcc is 5 [V (volt)]. The fluctuation of the output Vo due to the temperature at this time is as follows: dVo / dT = −5.20 × 10 ^ (8) T ^ (-4) / (2 + 3.69 × 10 ^ (7) T ^ (-3)) ^ (2) It becomes (11). And the temperature is -30 ° C, 25 ° C, and 120
From the equation (11), the output fluctuations due to the temperature at the temperature of ℃ are: −30 ° C. (T = 243K), dVo / dT = −
7.14 [mV / K] ・ At 25 ° C. (T = 298K), dVo / dT = −
5.72 [mV / K] -At 120 ° C (T = 393K), dVo / dT =-
It becomes 3.21 [mV / K].

(Temperature Characteristic of Position Sensor of Embodiment) Finally, the temperature characteristic of the position sensor of the above embodiment having the bias magnet 6 will be considered.

In the position sensor of the embodiment, the quadratic function in which the change in the resistance value of the semiconductor magnetoresistive element is μB (see the above equation (2)) in the intersection of the characteristic lines SL and SH described above.
To the μB linear function (see the above equation (3)), an offset magnetic field approximately equal to the change point is applied through the bias magnet 6. According to FIG. 4, this magnetic field strength is about “0.166T”. Further, according to the above experiment, when the offset magnetic field of "0.183T", which is the closest to the "0.166T", is applied, the output fluctuation width of the same position sensor decreases within "1 °". There is.

Therefore, in this case, assuming that the magnetic field strength of the offset magnetic field corresponding to the above-mentioned change point is Bc, the relationship between the resistance values R1 and R2 of each magnetic resistor and μB is that of the detected object (rotating shaft 3). When the position θ is θ << 0,
Corresponding to the case of θ≈0 and the case of θ >> 0, the following is obtained.

(1) In the case of θ << 0 In this case, the relationship of the magnetic field strength B is B1>Bc> B2, so that the resistance value R1 of the magnetic resistor on the high magnetic field side is R1.
Becomes R1 = (a + bcT ^ (-3/2) B1) Ro (12) from the above equation (6), and the resistance value R2 of the magnetic resistor on the other side in the low magnetic field is (5) above. From the formula, R2 = (1 + c ^ (2) T ^ (-3) B2 ^ (2)) Ro (13).

Further, the output Vo of the same position sensor at this time
Is obtained by substituting these equations (12) and (13) into the above equation (1), Vo = Vcc (1 + c ^ (2) T ^ (-3) B2 ^ (2)) / (a + 1 + bcT ^ (-3/2) B1 + c ^ (2) T ^ (-3) B2 ^ (2)) (14).

On the other hand, the temperature dependence of the output Vo is obtained by differentiating the equation (14) by the absolute temperature T, and dVo / dT = 1.5 cT ^ (-5/2) Vcc × (bB1- 2acT ^ (-3/2) B2 ^ (2) -bc ^ (2) T ^ (-3) B1B2 ^ (2)) / (a + 1 + bcT ^ (-3/2) B1 + c ^ (2) T ^ (- 3) B2 ^ (2)) ^ (2) (15)

In this equation (15), bB1-2acTo ^ (-3/2) B2 ^ (2) -bc ^ (2) To ^ at a temperature To in the temperature range in which the same position sensor is used. (-3) B1B2 ^ (2) = 0 (16) If the above constants a, b, and c are set, then dVo / dT = 0. In this case, in the case of T <To, dVo / dT <
0, and when T> To, dVo / dT> 0, and the temperature coefficient of output fluctuation is inverted before and after the temperature To. Therefore, according to the position sensor of the embodiment, the output fluctuation range can be suppressed by setting such constants.

Furthermore, in the case of the position sensor of the embodiment,
Since the magnetic field applied to the magnetoresistive body increases due to the application of the offset magnetic field, the denominator of the equation (15) becomes large. That is, the output fluctuation rate “dVo / d due to the above temperature”
The absolute value of “T” becomes smaller, and the effect of suppressing the fluctuation range is further promoted.

(2) In the case of θ≈0 In this case, the relationship of the magnetic field strength B is B1, B2> Bc, so that the two magnetic resistors are both placed in a high magnetic field, and their respective resistance values are set. R1 and R2 are as described in (6) above.
From the formulas, R1 = (a + bcT ^ (-3/2) B1) Ro ... (17) R2 = (a + bcT ^ (-3/2) B2) Ro ... (18), respectively.

The output Vo of the same position sensor at this time
Is obtained by substituting these equations (17) and (18) into the above equation (1), Vo = Vcc (a + bcT ^ (-3/2) B2) / {2a + bcT ^ (-3/2 ) (B1 + B2)} (19)

On the other hand, the temperature dependence of the output Vo is also obtained by differentiating the equation (19) by the absolute temperature T, and dVo / dT = 1.5Vcc × abcT ^ (-5/2) (B1- B2) / {2a + bcT ^ (-3/2) (B1 + B2)} ^ (2) (20).

Since B1≈B2 at the same position of the object to be detected (rotary shaft 3), the output fluctuation dVo /
dT also becomes dVo / dT≈0, and the variation of the output Vo with temperature is extremely small.

(3) In the case of θ >> 0 In this case, the relationship of the magnetic field strength B is B1 <Bc <B2. Therefore, the resistance value R1 of the magnetic resistor on the side under the low magnetic field is R1.
Is R1 = (1 + c ^ (2) T ^ (-3) B1 ^ (2)) Ro ... (21) from the above equation (5), and the resistance value of the other magnetic resistor placed in the high magnetic field. From the equation (6), R2 is R2 = (a + bcT ^ (-3/2) B2) Ro (22).

The output Vo of the same position sensor at this time
Is obtained by substituting these equations (21) and (22) into the above equation (1), Vo = Vcc (a + bcT ^ (-3/2) B2) / (a + 1 + c ^ (2) T ^ (-3) B1 ^ (2) + bcT ^ (-3/2) B2) (23)

On the other hand, the temperature dependence of the output Vo is also obtained by differentiating the equation (23) with the absolute temperature T, and dVo / dT = 1.5 cT ^ (-5/2) Vcc × (bB2- 2acT ^ (-3/2) B1 ^ (2) -bc ^ (2) T ^ (-3) B1 ^ (2) B2) / (a + 1 + c ^ (2) T ^ (-3) B1 ^ (2) + Bc ^ (2) T ^ (-3/2) B2) ^ (2) (24).

Also in this case, as in the case of θ << 0 in (1) above, the output fluctuation due to temperature is suppressed.
From the symmetry of the sensor structure, if the above equation (16) is satisfied at the position of θ = −θ ′, bB2-2acTo ^ (− 3 in the equation (24) at the position of θ = θ ′ is obtained. The condition of / 2) B1 ^ (2) -bc ^ (2) To ^ (-3) B1 ^ (2) B2 = 0 (25) is always satisfied.

In the position sensor of the same embodiment used in the above experiment, the detected object (rotating shaft 3) is θ = F. S. (50
When B1 and B2 at the position of () are assumed to be B1 = 0.11 [T] and B2 = 0.23 [T], respectively, and the power supply voltage Vcc is 5 [V (volt)] Output Vo temperature of -30 ° C, 25 ° C, and 1
The output fluctuations at 20 ° C. are as follows: dVo / dT = at −30 ° C. (T = 243K)
2.23 [mV / K] -At 25 ° C (T = 298K), dVo / dT =
0.38 [mV / K] ・ At 120 ° C (T = 393K), dVo / dT =-
It becomes 0.96 [mV / K]. These values are about 1/10 of the output fluctuation due to the temperature of the conventional position sensor calculated previously.

As described above, according to the non-contact type position sensor of the above embodiment, the bias magnet 6 causes the predetermined offset magnetic field corresponding to the change point of the magnetic field strength-resistance value characteristic of the magnetoresistive element 8 itself. By providing the magnetoresistive element 8, it is possible to preferably suppress the fluctuation of the output characteristic due to the temperature change without providing any special temperature compensation circuit.

Although not specifically performed as the measurement according to FIG. 5, the applied offset magnetic field corresponds to the change point of the characteristic of the magnetoresistive element 8 of "0.166".
It is not difficult to imagine that the output fluctuation range will be further reduced by setting "T".

Further, in the above-described embodiment, since the bias magnet 6 is separately arranged, it is possible to apply a predetermined offset magnetic field to the magnetoresistive body relatively easily and accurately. For example, in addition to adjusting the size of the bias magnet 6 to adjust the magnetic field strength thereof, a gap may be provided between the bias magnet 6 and the yoke 7 and the magnetic field strength may be adjusted by adjusting the gap. Can be adjusted.

The bias magnet 6 can also be formed by a so-called electromagnet. The point is that it is sufficient to apply a predetermined offset magnetic field to the magnetoresistive element 8 at least during power feeding to the element. In particular, when the bias magnet 6 is composed of an electromagnet, the adjustment of the magnetic field strength described above can be performed more easily and accurately.

By the way, in the embodiment, the magnetoresistive element 8 is used.
Although the bias magnet 6 is used as the means for applying the offset magnetic field to the above, the configuration illustrated in FIGS. 6 to 9 can also be adopted as the same means.

That is, according to the configuration illustrated in FIG.
An offset magnetic field according to the above-described embodiment can be applied to the magnetoresistive element 8 through the magnets 5, especially the additional portions 5a and 5b.

Also with the configuration illustrated in FIG. 7, an offset magnetic field according to the above-described embodiment can be applied to the magnetoresistive element 8 through the additional portions 5a and 5b of the magnet 5 as well.

Further, according to the configuration illustrated in FIG. 8, the magnetic substance 13 provided between the magnet 5 and the magnetoresistive element 8 increases the area in which the magnetic field emitted from the magnet 5 contributes to the magnetoresistive element 8. Will be done. Therefore, also in this case, the offset magnetic field according to the above-described embodiment can be applied to the magnetoresistive element 8.

Further, according to the structure illustrated in FIG. 9, the offset magnetic field according to the above embodiment is applied to the magnetoresistive element 8 through the portion 5c of the magnet 5 which overlaps with the center line of the rotation axis. Will be able to.

In particular, according to the configurations illustrated in FIGS. 6 to 9, the non-contact type position having the same temperature compensation function as that of the above-described embodiment in a more compact form which does not require the arrangement of the bias magnet. The sensor can be configured.

In the same embodiment, the semiconductor magnetoresistive body made of InSb is used as the material of the semiconductor magnetoresistive body. However, the magnetoresistive body may be a semiconductor having high mobility, and InAs, or GaAs or the like can also be appropriately adopted.

By the way, the above condition for suppressing the temperature fluctuation of the output Vo is not always achieved only by the above magnetic circuits. That is, as the characteristics of the semiconductor magnetic resistor itself, if the magnetic field strength at the point where the magnetic field strength-resistance value characteristic changes is small, that is, at the smaller magnetic field strength, the square characteristic (quadratic function of μB) and the first power As long as the semiconductor magnetic resistor has a magnetic field strength-resistance value characteristic that intersects with the characteristic (linear function of μB), the two magnetic resistors operate at the same time according to different characteristics even if the magnetic circuit is not provided. The condition is met.

In short, "at least when the object to be detected (rotary shaft 3) is displaced, the two magnetic resistors operate with different magnetic field strength-resistance value characteristics." By using it as a body, the above condition can be satisfied, and it becomes possible to suppress the fluctuation of the output characteristic due to the temperature change without providing any special temperature compensating circuit.

Further, the same condition for suppressing the temperature fluctuation can be satisfied by setting the magnetic force of the magnet 5 itself without separately providing the above-mentioned magnetic circuit. That is, as the same magnet 5, "at least in the state in which the detected body is displaced, the two magnetic resistance bodies are separated from each other in magnetic field strength-
By using the one set to a magnetic force capable of operating in a magnetic flux density region having different resistance characteristics, the same condition can be satisfied in the semiconductor magnetoresistive body, without providing any special temperature compensation circuit. It becomes possible to suppress the variation of the output characteristic due to the temperature change.

In all of the above, the case where the present invention is applied as a rotary position sensor to a position sensor for detecting the rotation angle of a detected object such as a throttle opening of an on-vehicle internal combustion engine without contact is described. However, the present invention is similarly applied to other linear position sensors, such as a position sensor that detects a linear movement amount of a detected object without contact, such as a valve stroke of the engine.

FIG. 10 shows an outline of a configuration in which the present invention is applied to the linear position sensor as still another embodiment of the non-contact type position sensor according to the present invention. Note that, also in FIG. 10, the same elements as those described above are denoted by the same reference numerals,
The duplicated explanation of those elements is omitted.

In the case of this position sensor (linear position sensor), the magnet 5 facing the magnetoresistive element 8 is
A shaft 14 which is linearly displaced in a manner shown by an arrow in FIG.
(This becomes the object to be detected).

However, in the magnetoresistive element 8, the magnet 5
Based on the resistance values of the two magnetoresistive bodies that change according to the magnetic field strength due to the relative positional relationship with the above, the partial pressure value from the connection point is taken out as the displacement information of the detected body. It is similar to the case of the example.

Therefore, even in such a position sensor, the magnetoresistive element 8 is passed through, for example, the bias magnet 6.
If the predetermined offset magnetic field is applied to
Even if no special temperature compensation circuit is provided, it is possible to preferably suppress the change in the output characteristic due to the temperature change.

Whether the linear position sensor shown in FIG. 10 or the above-described rotary position sensor, the magnet 5 and the magnetoresistive element 8 (or the bias magnet 6 are included) are accompanied by displacement of the object to be detected. It suffices that the phases of the facing surfaces are relatively displaced in the connecting direction of the two magnetic resistors, and it is not always necessary that the magnet 5 side is moved along with the displacement of the object to be detected. Absent. That is, the other magnetic resistance element 8 (or the bias magnet 6 is included) may be moved along with the displacement of the detected object.

[0103]

As described above, according to the non-contact type position sensor of the present invention, the fluctuation of the output characteristic due to the temperature change can be suitably suppressed without the need of any temperature compensation circuit. Like

Therefore, it becomes possible to output highly accurate information on the displacement amount (position) of the object to be detected, regardless of the ambient temperature.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a non-contact type position sensor according to the present invention.

FIG. 2 is a sectional view showing a horizontal sectional structure of the position sensor of the embodiment.

FIG. 3 is a circuit diagram showing an equivalent circuit of the position sensor of the embodiment.

FIG. 4 is a graph showing magnetic field strength-resistance value characteristics of a semiconductor magnetoresistive element.

FIG. 5 is a graph showing temperature-output characteristics of the conventional position sensor and the position sensor.

FIG. 6 is a schematic front view showing another embodiment of the non-contact type position sensor of the present invention.

FIG. 7 is a schematic front view showing another embodiment of the non-contact type position sensor of the present invention.

FIG. 8 is a schematic front view showing another embodiment of the non-contact type position sensor of the present invention.

FIG. 9 is a schematic front view showing another embodiment of the non-contact type position sensor of the present invention.

FIG. 10 is a schematic front view showing another embodiment of the non-contact type position sensor of the present invention.

[Explanation of symbols]

1 ... Housing, 2 ... Bearing, 3 ... Rotating shaft, 4 ... Holder, 5 ... Magnet, 6 ... Bias magnet, 7 ... Yoke, 8 ... Magnetoresistive element, 9 ... Lead wire, 10 ... Power supply terminal, 11 ... Ground terminal , 12 ... Output terminal, 13 ... Magnetic material, 14 ... Shaft.

Claims (7)

[Claims] 1. Two semiconductor magnetic resistors electrically connected in series, magnet means arranged at a position facing a surface on which the magnetic resistors are arranged, and the magnetic resistance according to displacement of an object to be detected. Displacement transmitting means for relatively displacing the phase of the opposing surfaces of the body and the magnet means in the connecting direction of the two magnetic resistors, one end of the magnetic resistors connected in series is grounded, and the other end is connected. And a connection point based on the resistance value of each magnetic resistor that changes according to the magnetic field strength due to the relative positional relationship between the fed magnetic resistor and the magnet means. Output means for taking out a partial pressure value from the device as displacement information of the detected object, and at least the two magnetic resistors in a magnetic flux density region having different magnetic field strength-resistance value characteristics in a state where the detected object is displaced. To work with Non-contact type position sensor, characterized in that it comprises a magnetic circuit, a. 2. The magnetic circuit includes biasing means for applying a predetermined offset magnetic field corresponding to the magnetic field strength at the point where the characteristic changes in the magnetic field strength-resistance value characteristic of the magnetic resistor itself to the magnetic resistor. The non-contact type position sensor according to claim 1, which is configured to include. 3. The non-contact type position sensor according to claim 2, wherein the bias means is a bias magnet arranged at a position facing the magnet means via the magnetic resistor. 4. The non-contact type position sensor according to claim 2, wherein the bias means is a magnetic body which is integrally added to the magnet means so as to increase the facing area of the magnet means with the magnetic resistor. 5. The bias means is a magnetic body interposed between the magnet means and the magnetoresistor so as to increase the area of participation of the magnetic field emitted from the magnet means in the magnetoresistor. Item 2. The non-contact type position sensor according to item 2. 6. A semiconductor magnetoresistive body electrically connected in series, magnet means arranged at a position facing a surface on which the magnetoresistive body is disposed, and the magnetic resistance according to a displacement of an object to be detected. Displacement transmission means for relatively displacing the phase of the opposing surfaces of the body and the magnet means in the connecting direction of the two magnetic resistors, and one end of the series connected magnetic resistors are grounded and the other end is grounded. And a connection point based on the resistance value of each magnetic resistor that changes according to the magnetic field strength due to the relative positional relationship between the fed magnetic resistor and the magnet means. In a non-contact type position sensor having an output means for extracting a partial pressure value from the device as displacement information of the detected body, at least when the detected body is displaced, the two magnetic resistors have different magnetic field strengths. − Operates according to resistance value characteristics A non-contact type position sensor characterized in that a magnetic resistance to be produced is used as the semiconductor magnetic resistance. 7. A semiconductor magnetic resistor, which is electrically connected in series, a magnet means arranged at a position facing a surface where the magnetic resistor is disposed, and the magnetic resistor according to displacement of a detected body. Displacement transmitting means for relatively displacing the phase of the opposing surfaces of the body and the magnet means in the connecting direction of the two magnetic resistors, and one end of the series connected magnetic resistors are grounded and the other end is grounded. And a connection point based on the resistance value of each magnetic resistor that changes according to the magnetic field strength due to the relative positional relationship between the fed magnetic resistor and the magnet means. In the non-contact type position sensor, the magnet means includes at least the two magnetic resistances in a state in which the detected body is displaced. The magnetic field strength between the bodies A non-contact type position sensor, which is set to a magnetic force capable of operating in magnetic flux density regions having different degrees-resistance value characteristics.