JPH0914908A - Magnetic type angle sensor - Google Patents

Abstract

PURPOSE: To compensate drop in output of a magnetic flux density detector and drop in magnetomotive force of a permanent magnet due to a temperature rise with a simple structure. CONSTITUTION: At least one magnetic gap 6a for detection is formed on magnetic path forming bodies 5a and 5b which let a magnetic flux pass according to a relative angular position of a subject 1 to form a magnetic path, and a magnetic flux density detector 7 is arranged in the magnetic gap 6a for detection. Moreover, at least one additional magnetic gap 6b is formed at a position along a surface containing the magnetic gap 6a for detection and a rotating shaft C of the subject 1 or at a position symmetrical with the surface and a thermosensible magnetic member 8 is arranged in the additional magnetic gap 6b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic angle sensor such as a throttle position sensor (TPS) for an internal combustion engine, which detects an angular displacement of a rotating body.

[0002]

BACKGROUND ART A magnetic angle sensor that obtains a sensor output proportional to the rotation angle of a detected object is disclosed in Patent Application No. 5 of 1993.
No. 05882 (International application PCT / FR91 / 009
73). The magnetic angle sensor disclosed in the above publication will be described below with reference to FIG.

FIG. 1A is a plan view of the magnetic angle sensor, and FIG. 1B is a sectional view taken along line BB of FIG. 1A. In the magnetic angle sensor shown in this figure, for example, a rotary shaft 1 made of a non-magnetic material, which is a detected object that interlocks with a throttle shaft of an engine, rotates about a rotation axis C. A cylindrical or annular magnetic member 2 is arranged on the outer periphery of the rotary shaft 1, and an annular permanent magnet 3 is fitted on the magnetic member 2. The magnetic member 2 and the permanent magnet 3 are fixed to the rotating shaft 1 with an adhesive or the like, and these rotate integrally with the rotating shaft 1 to form an annular rotating body as a whole.

The permanent magnet 3 has two semi-annular permanent magnets 3a and 3b having a semi-annular cross section in which magnetic domains magnetized in a lateral direction, for example, a radial direction, with respect to the rotation axis C are distributed in a circumferential direction. It is configured by being connected. The magnetic poles of the permanent magnet 3a are N poles on the outer peripheral side and S poles on the inner peripheral side, and the permanent magnets 3b are S poles on the outer peripheral side and N poles on the inner peripheral side, and are magnetized in the direction crossing the rotation axis C as a whole. It is an annular magnet.

A pair of semi-annular magnetic members 5a and 5b having a semi-annular cross section surrounds the permanent magnet 3 via a gap 4. A pair of magnetic members 5a and 5b
Are preferably homogeneously symmetrical. Both leg end surfaces of the magnetic members 5a and 5b are opposed to each other, and a pair of magnetic gaps 6a and 6b for magnetic flux density detection are provided.
Is formed. Preferably, the magnetic gaps 6a and 6
b is formed along a plane (center line BB of the sensor) passing through the rotation center C.

The magnetic members 5a and 5b form a magnetic path forming body that forms a fixed magnetic path including the magnetic gaps 6a and 6b. A Hall element 7 is arranged in the magnetic gap 6a to detect the magnetic flux density and output an electric signal representing the magnetic flux density. The center of rotation C is preferably substantially coincident with the arc centers of the magnetic members 5a and 5b.

In the magnetic type angle sensor having such a structure, the magnetic flux generated from the permanent magnet 3a has the dotted lines S1 and S.
As shown by 2, the permanent magnet 3b is reached via the fixed magnetic path formed by the magnetic members 5a and 5b. Therefore, the rotating shaft 1 rotates, and the magnetic gap 6a is generated according to the relative position (angle) relationship between the magnetic member 5 and the permanent magnet 3 which are carried by the rotating shaft 1 and rotate, and the magnetic member 5 which is the magnetic path forming body. The magnetic flux density of will change. The Hall element 7 generates an electric signal according to the magnetic flux density in the magnetic gap 6a, and the rotational position (angle) of the rotating body, that is, the rotating shaft 1 can be detected by this electric signal.

However, in such a magnetic angle sensor, there is a problem that the output of the Hall element 7 decreases and the magnetomotive force of the permanent magnets 3a and 3b decreases as the operating temperature rises. Then, the decrease in the output of the Hall element and the magnetomotive force of the permanent magnet due to such a temperature increase directly lowers the detection sensitivity of the sensor and deteriorates the detection accuracy.

In order to solve such a problem, a temperature compensation circuit using a diode as shown in FIG. 2 can be considered. In the temperature compensating circuit shown in the same figure, the Hall element 7 detects the magnetic flux density and indicates the voltages VOUT1 and VOU which represent it.
Outputs T2. The voltage division output VA of the voltage divider composed of the resistors R1 and R2 is supplied to the positive input terminal of the operational amplifier OP1. The output terminal of the operational amplifier OP1 is connected to one of the bias terminals of the Hall element 7, and the other bias terminal of the Hall element 7 is grounded via the series circuit of the diode D1 and the resistor R3. The voltage VB appearing at the cathode terminal of the diode D1 is proportional to the bias current flowing through the Hall element 7, and this voltage VB is supplied to the input terminal of the operational amplifier OP1.

Here, FIG. 3 shows the temperature dependence of the current-voltage characteristic of the diode D1. As shown in FIG. 3, in the diode D1, when the forward current IF is constant, the forward voltage VF decreases as the temperature rises, while
The characteristic is that the forward voltage VF increases as the temperature decreases. With such a characteristic, the voltage VB changes and the bias current flowing through the Hall element 7 changes, so that the temperature is compensated.

However, in the temperature compensation circuit using the diode as described above, good temperature compensation can be realized up to about 100 ° C., but there is a problem that good temperature compensation cannot be performed at 100 ° C. or higher.

[0012]

In view of the above problems of the prior art, it is an object of the present invention to have a good temperature compensation characteristic even at high temperature, and to always provide an accurate angle of the detected object. It is to provide a magnetic angle sensor that can detect a position with high accuracy.

[0013]

SUMMARY OF THE INVENTION A magnetic angle sensor according to the present invention is an annular magnet which is magnetized in response to the rotation of an object to be detected so as to have at least one pair of mutually equally divided magnetic pole surfaces on its outer surface. And a magnetic path forming body that surrounds the annular magnet and forms a fixed magnetic path that includes at least one detection magnetic gap, and a magnetic flux density detection means disposed in the detection magnetic gap. In the position sensor, the magnetic path forming body has at least one additional magnetic gap at a position along a surface including the detection magnetic gap and the rotation axis of the annular magnet or at a position symmetrical to the surface, A temperature-sensitive magnetic member is disposed in the additional magnetic gap.

[0014]

In the magnetic angle sensor having the above structure,
The temperature-sensitive magnetic member arranged in the additional magnetic gap changes the magnetic resistance of the entire fixed magnetic path according to the temperature to compensate the temperature characteristics of the Hall element and the permanent magnet.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic angle sensor according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 4 shows an embodiment of the magnetic angle sensor according to the present invention. Incidentally, the parts denoted by the same reference numerals as those in FIG. 1 are parts having the same configuration as the conventional example shown in the same figure, and the description of such parts will be omitted.

In the magnetic angle sensor shown in FIG. 4, one of the magnetic gaps formed between the end faces of both leg portions of the magnetic members 5a and 5b, for example, the magnetic gap 6a is used as the detection magnetic gap, and the other is used as the additional magnetic gap 6b. The temperature-sensitive magnetic member 8 is arranged or filled in this. The configuration other than the points described above has the same structure as the magnetic angle sensor shown in FIG.

In FIG. 4, the magnetic members 5a and 5b are
It is made of a soft magnetic material having a high magnetic permeability and a low magnetic hysteresis characteristic, and for example, annealed pure iron or nickel alloy, sintered iron, or nickel iron is used. As the temperature-sensitive magnetic member 8, a material having a Curie temperature and magnetic permeability lower than those of the materials used for the magnetic members 5a and 5b, such as ferrite, is used.

FIG. 5 shows the temperature dependence of the saturation magnetic flux density of ferrite. As shown in FIG. 5, the saturation magnetic flux density of ferrite decreases as the temperature rises. Since such ferrite has a low Curie temperature and is likely to change from a ferromagnetic material to a paramagnetic material, the change in magnetic permeability with temperature is large. Further, as described above, ferrite is used for the magnetic members 5a and 5a.
Since the Curie point is lower than that of the material used for b, the magnetic permeability has a greater temperature dependency than the magnetic members 5a and 5b.

Next, the principle of temperature compensation by the temperature-sensitive magnetic member will be described. In FIG. 4, the ferrite used as the temperature-sensitive magnetic member 8 has a high magnetic permeability at a low temperature and thus has a low magnetic resistance and easily passes a magnetic flux. On the other hand, at a high temperature, the magnetic permeability is low and a magnetic resistance becomes high, so that a magnetic flux is generated. It has the property of being hard to pass. On the other hand, in the magnetic members 5a and 5b made of a material having a high Curie point, the magnetic resistance is slightly decreased due to the temperature rise. Therefore, when the magnetic flux passing through the temperature-sensitive magnetic member 8 side decreases as the temperature rises, the magnetic flux passing through the Hall element 7 side increases correspondingly, and the detection output of the Hall element decreases due to the temperature rise and the magnetomotive force of the permanent magnet increases. Will be compensated for the decrease.

In the magnetic angle sensor according to the above embodiment, the temperature range of 100 ° C. or higher can be accurately compensated. Further, in the present embodiment, along the surface including the magnetic gap 6a and the rotation axis C of the rotating body (in the permanent magnet 3 and the magnetic member 2) (sensor center line BB),
Although the temperature-sensitive magnetic member 8 is arranged or filled in the magnetic gap 6b formed on the magnetic path forming body, the present invention is not limited to this, and as shown in FIG. A pair of magnetic gaps 6b1 and 6b2 are formed at positions symmetrical with respect to the surface including the magnetic gap 6a of the forming body and the rotation axis C of the rotating body (center line BB of the sensor), and the temperature-sensitive magnetic members 8a and 8b are formed. May be arranged respectively.

In the embodiment shown in FIGS. 4 and 6,
Although ferrite is used as the temperature-sensitive magnetic member, the present invention is not limited to this, and a material having a large temperature dependency of magnetic permeability may be used. Further, in the above-described embodiments and the like, the Hall element 7 is used as the magnetic flux density detecting means, but the present invention is not limited to this, and other magnetic flux density detecting means such as a magnetoresistive effect element may be used.

Regarding a specific application of the magnetic angle sensor according to this embodiment, a throttle position sensor can be obtained by connecting the rotary shaft 1 to a throttle valve of an internal combustion engine, for example. The magnetic angle sensor according to the above-described embodiments and the like can be further used as a position detecting means in an automatic machine tool, an automatic carrier machine, or the like, and can be preferably applied to factory automation (FA) or the like.

[0023]

As described above, in the magnetic sensor of the present invention, at least one magnetic path forming body that forms a magnetic path by passing a magnetic flux corresponding to the relative angular position of the detected object is used. One magnetic gap for detection is formed, a magnetic flux density detection element is arranged in the magnetic gap for detection, and further, a position along the plane including the magnetic gap for detection and the rotation axis of the object to be detected or symmetrical to the plane. Since at least one additional magnetic gap is formed at a certain position and the temperature-sensitive magnetic member is disposed in the additional magnetic gap, the output of the magnetic flux density detection element at high temperature can be reduced and the temperature can be reduced permanently. It is possible to correct the decrease in the magnetomotive force of the magnet, and it is possible to always detect the accurate angular position of the detected object.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a conventional magnetic angle sensor. 1A is a plan view of the sensor, and FIG. 1B is a cross-sectional view of FIG. 1A taken along line BB.

2 is a diagram showing a temperature compensation circuit of the magnetic angle sensor of FIG. 1. FIG.

3 is a voltage of a diode used in the circuit of FIG.
It is a figure which shows the temperature dependence of a current characteristic.

FIG. 4 is a diagram showing a first embodiment of a magnetic angle sensor according to the present invention, FIG. 4 (a) is a plan view of the sensor, and FIG.
4B is a sectional view taken along the line BB of FIG.

5 is a diagram showing temperature characteristics of saturation magnetic flux density of the temperature-sensitive magnetic member of FIG.

FIG. 6 is a view showing a second embodiment of the magnetic angle sensor according to the present invention, FIG. 6 (a) is a plan view of the sensor, and FIG.
6B is a sectional view taken along the line BB of FIG. 6A.

[Description of Signs of Main Parts]

 1 rotating shaft (object to be detected) 2, 5 magnetic member 3 permanent magnets 4, 6 magnetic gap 7 Hall element 8 temperature-sensitive magnetic member

Claims (8)

[Claims] 1. At least 1 in response to rotation of a detected object
An annular magnet magnetized so as to have a pair of mutually equally divided magnetic pole surfaces on the outer surface; and a magnetic path forming body that surrounds the annular magnet and forms a fixed magnetic path including at least one magnetic gap for detection. A magnetic position sensor comprising magnetic flux density detecting means disposed in the magnetic gap for detection, wherein the magnetic path forming body is a surface including the magnetic gap for detection and a rotation axis of the annular magnet. A magnetic angle sensor having at least one additional magnetic gap at a position along or along the plane, and a temperature-sensitive magnetic member disposed in the additional magnetic gap. 2. The annular magnet comprises at least two semi-annular members each having a semi-annular cross section in which magnetic domains magnetized in a radial direction are distributed in a circumferential direction. Magnetic angle sensor. 3. The magnetic path forming member is composed of at least two magnetic semi-annular members, and leg end surfaces of the magnetic semi-annular members face each other to form the detection and additional magnetic gaps. The magnetic angle sensor according to claim 3, wherein 4. The magnetic angle sensor according to claim 4, wherein the temperature-sensitive magnetic member is filled in the additional magnetic gap. 5. The magnetic angle sensor according to claim 1, wherein the magnetic flux density detecting means is a Hall element. 6. The magnetic angle sensor according to claim 1, wherein the temperature-sensitive magnetic member has a magnetic permeability smaller than that of the magnetic path forming member. 7. The magnetic angle sensor according to claim 1, wherein the temperature-sensitive magnetic member has a Curie temperature lower than that of the magnetic path forming member. 8. The magnetic angle sensor according to claim 1, wherein the temperature-sensitive magnetic member is ferrite.