JP3515339B2 - Angle sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angle sensor provided with a hard magnetic material.

[0002]

2. Description of the Related Art Generally, an angle sensor includes a rotating shaft, a rotor, which is a magnet made of a hard magnetic material, provided on the rotating shaft, and detects a change in magnetic flux from the magnet to determine the amount of rotation of the rotating shaft. And a detecting unit for detecting. When the rotor is an angle sensor made of a ferromagnetic material, a magnet made of a hard magnetic material for applying a magnetic flux to the ferromagnetic material is provided. Conventionally, ferrite magnets, alnico magnets (A1-Ni-Co-Fe-based magnets), Sm-Co-based magnets, Nd-Fe-B-based magnets, and the like have been used as hard magnetic materials for such angle sensors. Was.

[0003]

However, an angle sensor provided with an Sm-Co based magnet or an Nd-Fe-B based magnet has a magnet with 10 atom% or more of Nd or 8 atom% or more of Sm.
However, since the amount of expensive rare earth elements used is large, there has been a problem that the manufacturing cost of the angle sensor increases. In addition, an angle sensor including an Nd-Fe-B-based magnet has a large change in magnetic characteristics due to the temperature of the magnet,
There is a problem that a drift occurs in the output of the angle sensor and the output cannot be used as the angle sensor. Furthermore, a bonded magnet molded by compression molding or injection molding by mixing with a rubber or plastic binder, because the binder is present,
The density of the magnetic material relatively decreases, and the hard magnetic characteristics decrease. Further, there is also a problem that it cannot be used for an angle sensor used at a high temperature because the heat resistance of the binder is low.

On the other hand, an angle sensor equipped with a ferrite magnet has a lower magnet manufacturing cost than a magnet containing a rare earth element, but has a large absolute value of the temperature coefficient of magnetization.
There is a problem that a drift occurs in the output of the angle sensor and the output cannot be used as the angle sensor. Further, alnico magnets (A1-Ni-Co-Fe-based magnets) have a small absolute value of the temperature coefficient of magnetization and are low in manufacturing cost, but have a small coercive force, and thus have been difficult to use as angle sensors.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has at least an excellent hard magnetic characteristic at a low cost, and further has an angle provided with a magnet made of a hard magnetic material having an excellent temperature characteristic. It is intended to provide a sensor.

[0006]

In order to achieve the above object, the present invention employs the following constitution. An angle sensor of the present invention, hard made of a magnetic material, a compaction magnets solidifying and molding, and a detector for detecting a change in magnetic flux from the magnet, the hard magnetic material, Fe, Co, among Ni , An alloy containing at least one element T, an element R consisting of at least one of the rare earth elements, and B, and having an absolute temperature coefficient of magnetization when used in a shape having a permeance coefficient of 2 or more. 0.06 % in temperature range from room temperature to 80 ° C
/ K or less and the ratio of the residual magnetization (Ir) to the saturation magnetization (Is) (Ir / Is) is 0.6 or more .
Characterized by the following composition: T _x M _y R _z B _w However, T is Fe, Co, one or more elements of Ni
M represents one or more of Zr, Nb, Ta, and Hf.
R represents one or more rare earth elements
In addition, x, y, z, and w indicating the composition ratio are atomic%.
Where 86 ≦ x ≦ 92, 0.5 ≦ y ≦ 3, 3 ≦ z ≦ 7,3
≦ w ≦ 7.

Further, the hard magnetic material according to the present invention is characterized by comprising an alloy containing a soft magnetic phase having a coercive force of 500 Oe or less and a hard magnetic phase having a coercive force of 500 Oe or more, each at 10 vol (volume)% or more. In addition, the hard magnetic material according to the present invention includes a magnetic phase having a Curie temperature of 600 ° C. or more and a magnetic phase having a Curie temperature of 600 ° C. or less, respectively.
It is characterized by being made of an alloy containing 0 vol (volume)% or more.

The angle sensor according to the present invention is the angle sensor described above, wherein the hard magnetic material has a residual magnetization (Ir) of 9
0 emu / g or more, and the coercive force is 2 kOe or more. Further, the angle sensor of the present invention,
The angle sensor described above, wherein the hard magnetic material is a fine crystalline material having a particle size of 100 nm or less obtained by heat-treating an alloy having an amorphous phase as a main phase obtained by quenching a molten alloy. The phase is the main phase. Further, the angle sensor of the present invention is the angle sensor described above, wherein the hard magnetic material is heat-treated with an alloy powder having an amorphous phase as a main phase obtained by quenching a molten alloy. Thereby, it is characterized in that it is a consolidated body which is solidified and formed at the same time as crystallization.

Further, the angle sensor according to the present invention is the angle sensor described above, wherein a temperature rise rate at the time of the heat treatment is one.
0 ° C./min or more, the heat treatment temperature is 600 to 800 ° C., and the holding time is 1 to 60 minutes .

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The angle sensor according to the present invention includes a magnet made of a hard magnetic material and a detection unit that detects a change in magnetic flux from the magnet.

FIG. 1A shows an example in which the angle sensor according to the present invention is used for a rotary encoder 11, and the rotary encoder 11 is connected to a rotating shaft 13 according to the present invention. The rotor 14 includes a plurality of columnar magnets 15, 15... Made of a material and a rotating drum 16, and a detection unit 17 that is spaced apart from the outer peripheral surface of the rotor 14. The magnets 15, 15,... And the rotary drum 16 are joined by, for example, an adhesive. Further, the material of the rotating drum 16 is not particularly limited to a magnetic material, and for example, a metal material or the like can be used. The magnet 15 made of a hard magnetic material is shown in FIG.
As shown in (b), the rotating drum 1 is formed in a cylindrical shape having a permeance coefficient of about 2 or more.
The NS poles are arranged alternately along the circumference of No. 6. The magnet 15 has an absolute value of the temperature coefficient of magnetization of 0.06 % / K or less in a range of room temperature to 80 ° C. As the detection unit 17, any device can be used as long as it can detect a change in magnetic flux from the rotor 14. For example, a Hall element, a magnetoresistive element, a magnetoimpedance effect element, or the like can be used. . Further, the rotating shaft 13 is connected to the motor 12.
Further, the detecting unit 17 is connected to a measuring unit (not shown).

When the motor 12 rotates, the rotor 14 simultaneously rotates. At this time, since the rotor 14 is provided with a plurality of magnets 15, 15... The direction of the applied magnetic flux from the rotor 14 changes, and an output signal (a change in voltage, a change in current, etc.) corresponding to the change in the magnetic flux is sent from the detection unit 17 to the measurement unit, and the rotation of the motor 12 is changed. The amount is measured.

The hard magnetic material provided in the angle sensor of the present invention is an alloy containing at least one element T of Fe, Co, and Ni, an element R of at least one of rare earth elements, and B. , And the absolute value of the temperature coefficient of magnetization when used in a shape having a permeance coefficient of 2 or more is room temperature (2
0.06 % / K or less in the temperature range of 5 ° C.) to 80 ° C., and the residual magnetization (Ir) with respect to the saturation magnetization (Is).
(Ir / Is) is 0.6 or more.

By the way, the characteristics of the magnet material are represented by the second quadrant of the hysteresis curve, that is, the demagnetization curve. Since the magnet material after magnetization is under the opposite magnetic field created by its own remanent magnetization, ie, the demagnetizing field, its operating point (magnetic flux density (B) and demagnetizing field (H) of the material) is demagnetized. Given by one point p on the curve. Here, the value of B / μ ₀ H (dimensionless number) is expressed as permeance coefficient (p), p and origin O
The line between (OP) is called a permeance line. This permeance coefficient (p) or permeance line depends on the shape of the magnet, and decreases as the length in the magnetization direction decreases,
It becomes larger as it becomes longer, for example, p = 1.5
Are disc-shaped and those with p = 10 are prismatic. There is a relationship between the permeance coefficient (p) and the demagnetizing coefficient (N) represented by the following equation (I): p = (1-N) / N (I) Therefore, given the demagnetization curve and the shape of the magnet material, the operating point (B, H) is determined. The energy (U) of the static magnetic field generated by the magnet material is given by the following equation (II) U = BHV / 2 (II) (where V is the volume of the magnetic material). When the shape of the magnet material changes, the demagnetizing field,
That is, since the permeance line changes, the operating point p changes and the value of U changes. The value of U at the operating point p _m that way is maximized, the product of (BH) at that time is the maximum magnetic energy product ((BH) max).

For the angle sensor of the present invention, a hard magnetic material having excellent temperature characteristics, that is, having a small absolute value of the temperature coefficient of magnetization, is used in order to prevent the output from drifting due to a temperature change. Preferably, the hard magnetic material according to the present invention has an absolute value of a temperature coefficient of magnetization when used in a shape having a permeance coefficient of 2 or more as described above in a temperature range from room temperature (25 ° C.) to 80 ° C. 0.
Since it is as small as 0.6 % / K or less, the drift of the output of the angle sensor can be reduced.

Therefore, the hard magnetic material according to the present invention has Nd
Since the absolute value of the temperature coefficient of magnetization can be made smaller than that of the -Fe-B-based magnet, the output drift can be made lower than that of the conventional angle sensor using the Nd-Fe-B-based magnet. Further, the hard magnetic material according to the present invention has a larger coercive force than an alnico magnet, and is less expensive than an Sm-Co-based magnet conventionally used as having good temperature characteristics. Particularly, the hard magnetic material according to the present invention is obtained by adding 0.5 to 5 atomic% of Si by substitution of T element or by containing 0.5 to 20% of Co in T element as described later. It is possible to suitably realize a hard magnetic material having excellent temperature characteristics.

The hard magnetic material of the present invention has a coercive force of 50%.
A soft magnetic phase of 0 Oe or less and a hard magnetic phase of coercive force of 500 Oe or more may each contain 10 vol (volume)% or more. Thus, the coercive force is 500 Oe
It is preferable that the following soft magnetic phase and a hard magnetic phase having a coercive force of 500 Oe or more are included in the above-described range, since characteristics between the soft magnetic phase and the hard magnetic phase can be provided. 10 vo soft magnetic phase with coercive force of 500 Oe or less
If it is less than 1 (volume)%, the Nd required for the hard magnetic phase
And the like, and the residual magnetization also decreases, which is not preferable. If the hard magnetic phase having a coercive force of 500 Oe or more is less than 10 vol (volume)%, the coercive force is undesirably low. The preferred content of the soft magnetic phase having a coercive force of 500 Oe or less is 20 to 60 vol (volume)%.
The preferable content of the hard magnetic phase having a coercive force of 500 Oe or more is 40 to 80 vol (volume)%.

The hard magnetic material of the present invention may contain a magnetic phase having a Curie temperature of 600 ° C. or higher and a magnetic phase having a Curie temperature of 600 ° C. or lower, each at 10 vol. Curie temperature is 600
It is preferable that a magnetic phase having a magnetic phase of not lower than 600 ° C. and a magnetic phase having a Curie temperature of not higher than 600 ° C. in the above-mentioned range can provide intermediate properties between a soft magnetic phase and a hard magnetic phase. Since the Curie temperature of the bcc-Fe phase is around 770 ° C. and the Curie temperature of the R ₂ Fe ₁₄ B phase is around 315 ° C., the soft magnetic material in which the hard magnetic material of the present invention is involved in magnetization is used. In order to have two phases, a phase and a hard magnetic phase, it is necessary to include a magnetic phase having a Curie temperature of 600 ° C. or higher and a magnetic phase having a Curie temperature of 600 ° C. or lower. If the magnetic phase having a Curie temperature of 600 ° C. or higher is less than 10 vol (volume)%, the temperature change of magnetization when used at a relatively high permeance becomes large, which is not preferable. The magnetic phase having a Curie temperature of 600 ° C. or less
If the content is less than vol (volume)%, the amount of the hard magnetic phase is reduced, so that the coercive force is lowered, which is not preferable. The preferred content of the magnetic phase having a Curie temperature of 600 ° C. or higher is 20 to
60 vol (volume)%, Curie temperature is 600 ° C
The preferred content of the following magnetic phase is 40 to 80 vol (volume)%.

The hard magnetic material of the present invention mainly contains a fine crystalline phase having an average crystal grain size of 100 nm or less, and the fine crystalline phase includes a bcc-Fe phase having an average crystal grain size of 100 nm or less. And an R ₂ Fe ₁₄ B phase having an average crystal grain size of 100 nm or less is precipitated. Furthermore, the hard magnetic material of the present invention forms a nano-multiphase structure of the fine crystalline phase of the bcc-Fe phase and the R ₂ Fe ₁₄ B phase and the remaining amorphous phase. Further, the hard magnetic material of the present invention is obtained by subjecting an alloy mainly composed of an amorphous phase obtained by quenching the molten alloy having the above structure to heat treatment. Further, the hard magnetic material according to the present invention preferably has a coercive force of 2 kOe or more. The control of the average crystal grain size of the crystalline phase in the hard magnetic material and the concentration of each atom in each phase as described above controls the heat treatment conditions when the amorphous alloy is heat-treated to obtain the hard magnetic material. This can be achieved by doing
The heat treatment conditions include a temperature rising rate, a heat treatment temperature (annealing temperature), and a holding time thereof.

The hard magnetic material according to the present invention can be represented by the following composition formula. TxMyRzBw T in the above composition formula represents at least one element of Fe, Co, and Ni. These elements are the main components of the hard magnetic material according to the present invention, are elements that carry magnetism, and are 90 emu.
In order to realize the remanent magnetization (Ir) of / g or more, the concentration of T needs to be 50 atom% or more. Also, 100e
In order to obtain a residual magnetization (Ir) of not less than mu / g, the concentration of T is preferably not less than 80 atomic%. As the composition ratio x of T increases, the saturation magnetization (Is) increases accordingly. High remanent magnetization (Ir) of 120 emu / g or more
In order to realize, the saturation magnetization (Is) must be at least 1
30 emu / g is required, and in order to satisfy this, the concentration of T is desirably from 86 atomic% to 92 atomic%. In the hard magnetic material of the present invention, it is necessary that Fe is contained as at least a part of the element T. It is preferable that at least 50% or more of Fe is contained in the element T.

M in the above composition formula is Zr, Nb, Ta, H
f represents one or more elements, and these elements have high amorphous forming ability. In the hard magnetic material according to the present invention, by adding M, an amorphous phase can be formed even when the rare earth element (R) has a low concentration. When the composition ratio y of the element M is increased by the rare earth element (R) substitution,
Accordingly, the remanent magnetization (Ir) increases, but the coercive force (iHc) decreases, and the hard magnetic characteristics change to soft magnetic characteristics. Further, when the amorphous forming element (M) is increased by the substitution of the element (T) that carries the magnetism, the saturation magnetization (Is) and the residual magnetization (Ir) decrease. Therefore, the upper limit of the addition amount of the element M is preferably 10 atomic%, and in order to obtain good hard magnetic properties, it is preferably in the range of 0.5 atomic% to 3 atomic%, more preferably 1.5 atomic%. % To 2.5 atomic%
It is desirable to do the following.

R in the above composition formula is a rare earth metal (Sc,
Y, La, Ce, Pr, Nd, Pm, Sm, Eu, G
d, Tb, Dy, Ho, Er, Tm, Yb, and L
u) represents one or more elements of An intermetallic compound R ₂ Fe ₁₄ B ₁ which precipitates when an amorphous alloy containing R, Fe and B is heated at an appropriate temperature in the range of 600 to 900 ° C.
Is for imparting excellent hard magnetic properties to the material of the present invention, and the amount of R added is preferably 10 atomic% or less. As the composition ratio z of R increases, the saturation magnetization (Ir) decreases accordingly. In order to obtain a high residual magnetization (Ir) of 100 emu / g or more, the saturation magnetization (Is) needs to be at least 130 emu / g, and to satisfy this, the concentration (z) of R is 10 atomic% or less. It is desirable. R is an element that easily forms an amorphous phase. If the composition ratio of R is too small, a good amorphous phase or fine crystalline phase cannot be obtained. Is desirable. Further, when part or all of R is composed of Nd and / or Pr, higher hard magnetic characteristics can be obtained.

B in the above composition formula is an element that easily forms an amorphous phase. Further, the amorphous phase containing Fe and B is
The compound R ₂ Fe ₁₄ B, which precipitates when heat-treated at an appropriate temperature in the range of ９００900 ° C., imparts hard magnetic properties to the material of the present invention. In order to obtain a good amorphous phase or fine crystalline phase, the concentration of B is desirably set to 3 atomic% or more. However, as the B composition ratio (w) increases, the saturation magnetization (Is), Remanent magnetization (Ir) and coercive force (iH
Since c) is reduced, in order to obtain good hard magnetic properties, the concentration of B is desirably 20 at% or less, preferably 7 at% or less, more preferably 5 at% or less.

In the hard magnetic material of the present invention, if Co is contained in the T element in addition to Fe, the absolute value of the temperature coefficient of magnetization when used in a shape having a permeance coefficient of 2 or more can be reduced. It is preferable in that it can be performed. The reason is that if Co is contained in the T element, the Curie temperature rises, so that the temperature change of magnetization and coercive force is small, and the squareness ratio of magnetization is high, so that the temperature change of magnetic characteristics is small. And this Co becomes bcc-
This is because the solid solution also forms a solid solution in the Fe phase, so that the temperature change of the residual magnetization is reduced. If the content of Co is too large, the magnetic properties are deteriorated. Therefore, the content of Co is preferably 50 atomic% or less, more preferably 0.5 atomic% or more and 30 atomic% or less, and still more preferably 0.5 atomic% or more and 20 atomic% or less. And it is preferable to appropriately set according to the composition of the alloy, heat treatment conditions, and the like.

In the hard magnetic material of the present invention, Si
Is added by replacing the T element, the magnetic properties, particularly the coercive force (i
Hc), and the maximum magnetic energy product ((BH) max)
Can be further improved, and the absolute value of the temperature coefficient of magnetization when used in a shape having a permeance coefficient of 2 or more can be reduced. If the addition amount of Si is too large, the composition ratio of the T element becomes low, so that the magnetic properties of the hard magnetic material are rather deteriorated. Therefore, the content of Si is preferably 0.5 atomic% or more and 5 atomic% or less, more preferably 0.5 atomic% or less. It is preferably in the range of at least atomic% and not more than 3 atomic%, and is preferably set as appropriate according to the composition of the alloy, heat treatment conditions, and the like.

Next, the hard magnetic material according to the present invention can be manufactured as follows. First, a method for obtaining an alloy mainly composed of an amorphous phase is a method in which a molten alloy is sprayed onto a rotating drum to rapidly cool and form a thin ribbon, or the molten alloy is jetted into a cooling gas to be rapidly cooled in a droplet state. And a liquid quenching method such as a method of forming into a powder, or a method of sputtering or CVD. Also,
The heat treatment of the amorphous alloy can be performed using any heating means. For example, when obtaining a compact made of the hard magnetic material of the present invention, first, the amorphous alloy is powdered, and A method in which the powder is pressure-formed by hot pressing and heat-treated at an appropriate temperature increasing rate and heat-treating temperature (annealing temperature) at the same time can be preferably used.

The heating rate during the heat treatment is 10 K / min or more,
It is preferably set in the range of 100 K / min or more according to the composition of the amorphous alloy. Heating rate during heat treatment is 1
If it is less than 0 K / min, the crystal grains precipitated in the alloy by heat treatment become coarse, so that the exchange between the soft magnetic phase (bcc (body-centered cubic structure) -Fe) and the hard magnetic phase (R ₂ Fe ₁₄ B) is performed. It is not preferable because the coupling characteristics are deteriorated and the hard magnetic characteristics are deteriorated. Further, by setting the heating rate during the heat treatment to a range of 100 K / min or more, it is possible to improve the characteristics by making the microstructure uniform and to shorten the time required for the heat treatment step and the manufacturing step. Note that the upper limit of the heating rate is set to about 200 K / min due to restrictions on the apparatus.

Heat treatment temperature during heat treatment (annealing temperature)
Is preferably 600 to 800 ° C., more preferably 65
The range of 0 to 750 ° C. and the holding time (heat treatment time) are preferably in the range of 1 to 60 minutes, more preferably 2 to 5 minutes, and are preferably set according to the composition of the amorphous alloy. If the heat treatment temperature is lower than 600 ° C., R ₂ Fe ₁₄ which is responsible for hard magnetic properties
Since the precipitation amount of the B phase is small, sufficient hard magnetic properties cannot be obtained, which is not preferable. On the other hand, if the heat treatment temperature exceeds 800 ° C., other precipitates precipitate and the hard magnetic properties are deteriorated, which is not preferable.

Further, as a heat treatment method for producing a magnet made of a hard magnetic material used for an angle sensor, a plasma sintering method can be used in addition to the above-described hot press method. FIG. 2 shows a main part of an example of the spark plasma sintering apparatus. The spark plasma sintering apparatus of this example includes a cylindrical die 21, an upper punch 22 inserted into the die 21, and a lower die 22. Support the punch 23 and the lower punch 23,
A punch electrode 24 serving as one electrode when a pulse current to be described later flows, a punch electrode 25 pressing the upper punch 22 to the lower side, and serving as the other electrode through which the pulse current flows, and being sandwiched between upper and lower punches 22 and 23. And a thermocouple 27 for measuring the temperature of the raw material powder 26. A mold corresponding to the shape of the magnet to be obtained is formed on a surface where the upper punch 22 and the lower punch 23 oppose each other. Further, a main part of the above-described spark plasma sintering apparatus is housed in a chamber (not shown). This chamber is connected to a vacuum evacuation device and an atmosphere gas supply device (not shown), and the raw material powder (granules) 26 filled between the upper and lower punches 22 and 23 is converted into a desired gas such as an inert gas atmosphere. It is configured so that it can be maintained in an atmosphere.

In order to manufacture a compact which is a magnet provided in an angle sensor using the discharge plasma sintering apparatus having the above-described structure, a raw material powder for molding is prepared. This raw material powder 26
The amorphous alloy of a predetermined composition is melted and then cast by a casting method, or by a quenching method using a single roll or twin rolls, and further by a submerged spinning method or a solution extraction method, or by a high-pressure gas spraying method. Bulk, ribbon,
It can be obtained by a process of producing various shapes such as a linear body and a powder, and a process of pulverizing and pulverizing a material other than a powder.

Next, after preparing the raw material powder 26 having a predetermined composition, the raw material powder 26 is put between the upper and lower punches 22 and 23 of the discharge plasma sintering apparatus shown in FIG. At the same time as applying pressure from above and below with the punches 22 and 23, a pulse current as shown in FIG. 3, for example, is applied to the raw material powder 26 and heated to form a sintered body having a desired shape. In this discharge plasma sintering process, the temperature of the raw material powder 26 can be quickly raised at a predetermined speed by the supplied current, and the temperature of the raw material powder 26 can be strictly controlled according to the value of the supplied current. The temperature can be controlled much more accurately than heating by sintering, and sintering can be performed under ideal conditions as designed in advance.

In the plasma sintering method, the sintering temperature is required to be 300 ° C. or higher in order to solidify and form the raw material powder 26, and to obtain excellent hard magnetic characteristics,
It is preferable that the temperature be in the range of 0 ° C. to 800 ° C.

In the present invention, the heating rate at the time of sintering is 10 sec.
C./min or more is preferable, and 40.degree. C./min or more is more preferable. Regarding the pressure during sintering, if the pressing force is too low, a sintered body cannot be formed, so that 3 t / c
m ² or more is preferable.

The compact thus obtained has the same composition as the amorphous alloy used as the raw material powder, and therefore has excellent hard magnetic properties at room temperature and is used as a magnet for an angle sensor. Can be used.

The above angle sensor is made of an alloy containing at least one element T of Fe, Co and Ni, one or more elements of rare earth elements R and B, and has a permeance coefficient of 2 or more. A magnet made of a hard magnetic material having an absolute value of a temperature coefficient of magnetization of 0.06 % / K or less in a temperature range from room temperature (25 ° C.) to 80 ° C. when used in the above shape; Since this hard magnetic material has the same or better temperature characteristics than conventional ferrite and Nd-Fe-B magnets, it can prevent output drift due to temperature change when used in an angle sensor. So you can
The reliability of detection accuracy can be improved. Further, since the shape of the magnet can be reduced, the shape of the angle sensor can be reduced. Further, in the above-described hard magnetic material, the ratio of the residual magnetization (Ir) to the saturation magnetization (Is) (Ir / Is) is 0.6 or more, and the maximum magnetic energy ((BH) max) can be increased. Therefore, the detection accuracy of the angle sensor can be greatly improved.

Since the above angle sensor is provided with a hard magnetic material having a residual magnetization (Ir) of 90 emu / g or more and a coercive force of 2 kOe or more, the detection accuracy of the angle sensor can be greatly improved. Can be.

The hard magnetic material according to the present invention mainly contains a fine crystalline phase having an average crystal grain size of 100 nm or less, and the fine crystalline phase includes a bcc-Fe phase having an average crystal grain size of 100 nm or less. Since the R ₂ Fe ₁₄ B phase having an average crystal grain size of 100 nm or less is precipitated, the soft magnetic phase (b
cc (body-centered cubic structure) -Fe) and a hard magnetic phase (R ₂ F)
e ₁₄ B) has improved exchange coupling characteristics, and the residual magnetization (I
r), squareness ratio (Rs), coercive force (iHc), and maximum magnetic energy product ((BH) max) are increased, and excellent hard magnetic properties are obtained. Specifically, the remanent magnetization (Ir) is 12
Hard magnetic material of 0 emu / g or more, squareness ratio (Rs) of 0.
Hard magnetic material of 6 or more, hard magnetic material having coercive force (iHc) of 2 kOe or more, maximum magnetic energy product ((BH) max)
Can achieve an excellent hard magnetic material exceeding 100 kJ / m ^3, and the detection accuracy of the angle sensor can be improved.

Further, the angle sensor provided with the above-described hard magnetic material can obtain excellent hard magnetic characteristics even when the content of the rare earth element R is reduced, so that an Sm-Co based magnet or Nd-Fe
-The manufacturing cost can be lower than that of an angle sensor using a B-based magnet. Further, the hard magnetic material used for the angle sensor described above is obtained by quenching a molten alloy and obtaining a powder of an alloy having an amorphous phase as a main phase by heat treatment, thereby consolidating simultaneously with crystallization. Since it is a body, a magnet having a free shape can be easily manufactured, and the degree of freedom in designing an angle sensor can be improved.

[0039]

【Example】

(Experimental Example 1) A quenched ribbon alloy of various compositions was heat-treated to produce a hard magnetic material as follows. First, an ingot is manufactured by an arc melting method, and a melted metal is blown out from a narrow nozzle having a slit diameter of about 0.3 mm onto a Cu roll rotating in an Ar atmosphere, thereby obtaining a thickness of about 20 μm. A quenched ribbon alloy was prepared. Next, the obtained quenched ribbon alloy is heated in an infrared image furnace of 1 × 10 ⁻² Pa or less at a heating rate of 180 K / min, and heat-treated at an annealing temperature of 750 ° C. for about 180 seconds. The obtained strip alloy sample (Example) was obtained. The compositions of the thin strip alloy samples obtained here are Fe ₇₆ Co ₁₀ Nb ₂ Pr ₇ B ₅ and Fe ₆₆ Co ₂₀ N which are all within the scope of the present invention.
It was a thin strip alloy having a composition of b ₂ Pr ₇ B ₅ and Fe ₈₄ Nb ₂ Pr ₇ B ₅ Si ₂ .

FIGS. 4 to 6 show that the obtained thin strip alloy sample of the embodiment was measured using a VSM (vibrating sample magnetometer).
Room temperature to about 220 ° C. in an applied magnetic field of 10 kOe and in vacuum
5 shows the measurement results of the demagnetization curve (second quadrant) at. FIG.
In FIG. 6, A is a straight line having a permeance coefficient (p) of 10 (a prismatic shape), and B is a straight line having a p of 1.5 (a disk shape). FIG. 7 shows the relationship between the magnetic properties and the temperature of the ribbon alloy sample of the example, the remanent magnetization (Ir) and the coercive force (iHc) obtained from the demagnetization curve (second quadrant).
5 shows the temperature change.

Table 1 shows the magnetic properties at room temperature of the ribbon alloy samples of the examples. In Table 1, Ir / Is is a ratio (square ratio) of the residual magnetization to the saturation magnetization. Table 2 shows the room temperature to about 490 of the ribbon alloy sample of the example.
Temperature coefficients of Ir and iHc at K, p = 1.5,
It shows the temperature coefficient of Ir from room temperature to about 490K when the shape is such that p = 10. Further, as a comparative example, a conventional ferrite magnet and an Nd—Fe—B-based (Nd ₂ Fe ₁₄ B)
FIG. 8 shows the relationship between the magnetic characteristics of the magnet and the temperature.
Table 2 shows the Ir temperature coefficient of this conventional magnet.

[0042]

[Table 1]

[0043]

[Table 2]

FIG. 7 and Table 2 show that Ir and iHc tend to decrease as the temperature increases in the ribbon alloy sample of the example and the magnet of the comparative example. Regarding the temperature coefficient of iHc (diHc / dT), the Fe ₈₈ Nb ₂
A Pr ₅ B ₅ samples of a composition is -0.43% / K, is a value close to the value of the Nd-Fe-B based magnet of Comparative Example (-0.4% / K), Co and Si In the thin strip alloy sample of the example to which N was added, -0.28 to -0.36% / K, which was N in the comparative example.
It is recognized that the value is smaller than that of the d-Fe-B based magnet. The reason why the temperature coefficient of iHc is reduced by adding Co in this manner is considered to be due to an increase in the Curie temperature of the hard magnetic phase.

With respect to the temperature coefficient of Ir (dIr / dT), the sample having the composition of Fe ₈₈ Nb ₂ Pr ₅ B ₅ of the embodiment was −
Nd-Fe-B based magnet of the comparative example (a magnet having a composition of Fe ₇₇ Nd ₅ B ₈ , (Fe _0.9 Co _0.1 )
₇₇ Nd ₁₅ B ₈ ) is -0.11--
It can be seen that it is lower than 0.18% / K. This is because, in the magnet of the comparative example, the phase involved in the magnetization is only the hard magnetic phase, whereas in the ribbon alloy sample of the example, the hard magnetic phase and the soft magnetic phase having a small temperature change rate of the magnetization ( (bcc-Fe phase). Moreover, the temperature coefficient of Ir of the ribbon alloy sample of the example to which Co or Si was added was −
It is recognized that the value is as small as 0.02% / K. Further, FIG. 5 shows that the sample having the composition of Fe ₆₆ Co ₂₀ Nb ₂ Pr ₇ B ₅ has a small magnetization temperature change particularly in the region of p = 10 or more and has excellent temperature characteristics.

FIG. 8 shows a sample of the thin strip alloy according to the embodiment, where p = 1.
7 is a graph obtained from the demagnetization curves shown in FIGS. 4 to 6, showing the relationship between the temperature and Ir when each of them is used in the shape where p = 10. For comparison, the conventional Sm-C
FIG. 8 shows the relationship between the temperature and Ir when the o magnet and the Nd—Fe—B magnet (composition of Nd ₂ Fe ₁₄ B) were used in the shapes of p = 1.5 and p = 10, respectively. Shown. FIG. 9 shows Fe ₈₈ Nb within the composition range of the present invention.
₂ Nd ₅ B ₅ having a composition of sintered bulk (alloy compacts) shows the relationship between the permeance coefficient and temperature coefficient of the ribbon alloy samples of the sample and Fe ₈₆ Nb ₂ Pr ₇ B ₅ a composition. For comparison, FIG. 9 shows the relationship between the permeance coefficient and the temperature coefficient of a conventional Nd—Fe—B-based magnet (composition of Nd ₂ Fe ₁₄ B).
Shown along with.

From Table 2 and FIGS. 7 to 9, when p = 1.5 and the permeance coefficient is low, a sample having a composition of Fe ₈₄ Nb ₂ Pr ₇ B ₅ Si ₂ which is an example to which Si is added is used. The temperature coefficient is -0.17% / K, and the composition of Fe ₇₆ Co ₁₀ Nb ₂ Pr ₇ B ₅ which is an example to which Co is added, and Fe ₆₆
Co ₂₀ Nb ₂ Pr ₇ temperature coefficient of the sample B ₅ having the composition, respectively -0.20% / K, was -0.33% / K, also, samples of Fe ₈₈ Nb ₂ Pr ₅ B ₅ having the composition Has a relatively high temperature coefficient of -0.38% / K, which is the same as that of the conventional material. When used with a high permeance coefficient of p = 10, the Fe ₈₈ N
b ₂ Nd ₅ samples the temperature coefficient of the B ₅ becomes composition -0.12%
/ K, which is about the same as the temperature coefficient of the conventional Nd-Fe-B-based magnet, but the Fe ₈₄ Nb of the embodiment to which Si is added.
The sample having a composition of ₂ Pr ₇ B ₅ Si ₂ was −0.05% / K, and Fe ₆₆ Co ₂₀ Nb ₂ Pr ₇ B of the example to which Co was added.
It can be seen that the sample having a composition of ₅ is -0.08% / K, which indicates that the change in magnetic properties with temperature is small. Further, when used in a shape where p = 10, the ribbon alloy sample of the example, particularly the sample having a composition of Fe ₆₆ Co ₂₀ Nb ₂ Pr ₇ B _5, has a temperature in a practical temperature range from room temperature to about 80 ° C. The absolute value of the coefficient is small, has the same excellent temperature characteristics as the Sm-Co based magnet of the comparative example, and
It can be seen that the temperature characteristics are superior to the Nd ₂ Fe ₁₄ B-based magnet of the comparative example.

As shown in Table 2 and FIGS. 7 to 9, when the sample having the permeance coefficient of 2 or more is used at room temperature to 8
In a temperature range of 0 ° C., the absolute value of the temperature coefficient of the Nd ₂ Fe ₁₄ B-based magnet of the comparative example is almost the same as or smaller than the absolute value. In particular, when the permeance coefficient is 10 or more, the temperature coefficient is 0.1 % / K, the absolute value of the temperature coefficient is smaller than that of the Nd ₂ Fe ₁₄ B-based magnet of the comparative example, and the temperature characteristics are excellent.

(Experimental Example 2) The temperature change of magnetization of a hard magnetic material obtained by subjecting an amorphous alloy ribbon having a composition of Fe ₈₈ Nb ₂ Pr ₅ B ₅ to a heat treatment at an annealing temperature of 750 ° C. was examined. Was. The temperature change of the magnetization of the hard magnetic material obtained by heat-treating the amorphous alloy ribbon having the composition of Fe ₈₈ Pr ₇ B ₅ after quenching at an annealing temperature of 650 ° C. was examined. The result is shown in FIG.
Shown in FIG. 10 is a diagram showing the temperature change of the magnetization of a hard magnetic material having a composition of Fe ₈₈ Nb ₂ Pr ₅ B ₅ and a hard magnetic material having a composition of Fe ₈₈ Pr ₇ B ₅ . As shown in FIG. 10, the magnetization decreases in two steps as the temperature increases. This indicates that there are two phases involved in the magnetization of the hard magnetic material. Further, since the degree of the decrease in magnetization changes around 315 ° C., the vicinity of Fe
_This is the Curie temperature of the ₁₄ Nd ₂ B phase, and the degree of the decrease in magnetization changes around 770 ° C., which indicates that the Curie temperature of the bcc-Fe phase is around this temperature. Here, the absence of the magnetization step due to the amorphous phase is considered to be due to the low magnetization and the small volume fraction.

FIG. 11 shows the above-mentioned Fe ₈₈ Nb ₂ P
The second quadrant of the magnetization curve of a hard magnetic material having a composition of r ₅ B _{5 and} a hard magnetic material having a composition of Fe ₈₈ Pr ₇ B ₅ is shown. As shown in FIG. 11, the magnetization curve has no steps similar to the magnetic material composed of a single phase, and a fine soft magnetic phase and a hard magnetic phase are magnetically coupled. It turns out that it is an exchange coupling magnet.

(Experimental Example 3) As in Experimental Example 1, the atomic composition ratio was Fe ₈₈ Nb ₂ Nd ₅ B ₅ and Fe ₇₃ Co ₁₅ Nb ₂ N.
_{d 5 B 5, Fe 79 Co} 10 Nb 2 Nd 4 B 5, Fe 89 Nb 2 Nd
_{5 B 4, Fe 78 Co 10} Nb 2 Nd 5 B 5, Fe 89 Nb 2 Nd 4
A quenched ribbon alloy of B ₅ and Fe ₉₀ Nb ₂ Nd ₅ B ₃ having a thickness of about 20 μm was produced. Next, the obtained quenched ribbon was pulverized in the air using a rotor mill. Among the obtained powders, those having a particle size of 53 to 105 μm were selected and used as raw material powders in the subsequent steps. About 2g
The above raw material powder was filled into a die made of WC by using a hand press, and then loaded into a die 21 shown in FIG. 3, and the inside of the chamber was punched up and down in an atmosphere of 3 × 10 ⁻⁵ torr. Pressurizing at 22 and 23 and sintering by applying a pulse wave to the raw material powder from the current supply device,
A sintered body was obtained. Next, a plurality of the sintered bodies were cut into a cylindrical shape to obtain magnets 15, 15,... Used for the rotary encoder 11 in FIG. As shown in FIG. 3, the pulse waveform at this time was such that after 12 pulses were passed, two pulses were paused, and the raw material powder was heated at a maximum current of 4700 to 4800A. The sintering conditions are as follows: the sample is heated from room temperature to the sintering temperature while applying a pressure of 6.5 t / cm ² ,
This was done by holding for minutes. The heating rate during sintering is 4
0 ° C./min (0.67 K / sec). Are magnetized to produce a plurality of magnets 15, 15... Having a diameter of 0.5 mm and a length of 1 mm as shown in FIG. The magnets 15, 15... Are arranged so as to cover the circumference of the rotary drum 16, thereby producing a rotor 14. Using this rotor 14, a rotary encoder 11 as shown in FIG. Note that a Hall element was used for the detection unit 17 of the rotary encoder 11 manufactured here.

FIG. 12 shows a change in the output voltage from the detection unit when the operating temperature of this rotary encoder is increased from room temperature (25 ° C.) to 125 ° C. Also, the change amount (dT) of the output voltage with respect to the change amount (dT) of the operating temperature
Table 3 shows dV / dT, which is the ratio of V). Table 3 shows that the conventional Nd ₂ Fe ₁₄ B-based magnet, ferrite magnet, S
The dV / dT of the rotary encoder manufactured using the mCo ₅ magnet is also shown.

As is evident from Table 3, the rotary encoder using the magnet made of the hard magnetic material having the atomic composition of the present invention has a larger diameter than the one using the Nd ₂ Fe ₁₄ B-based magnet and the ferrite magnet. It can be seen that dV / dT is small and drift of the output voltage of the rotary encoder is small. Also, when compared to those using the SmCo ₅ magnets, but dV / dT is almost the same, SmCo ₅ magnets due to the high content of Sm is a rare earth element, higher production cost of the magnet, a rotary encoder Manufacturing costs cannot be reduced. Further, as is clear from FIG. 12, the rotary encoder provided with the magnet made of the hard magnetic material containing Co has a larger output voltage value than the one not containing Co and increases the detection accuracy of the rotary encoder. It becomes possible.

[0054]

[Table 3]

The technical scope of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present invention.
For example, in the embodiment, the example in which the angle sensor of the present invention is applied to a rotary encoder has been described. However, the present invention is not limited to this, and is used for a sensor for an anti-block system of an automobile and a sensor for measuring the amount of rotation. be able to.

[0056]

As described above in detail, the angle sensor of the present invention comprises at least one element T of Fe, Co, and Ni, and at least one element R of one or more rare earth elements.
The alloy has an absolute value of the temperature coefficient of magnetization when used in a shape having a permeance coefficient of 2 or more.
A magnet made of a hard magnetic material of 0.06 % / K or less in a temperature range of room temperature to 80 ° C. is provided. This hard magnetic material has the same temperature characteristics as a conventional ferrite or Nd—Fe—B magnet. Also, since it is excellent, it is possible to prevent an output drift due to a temperature change when used for an angle sensor, so that the reliability of detection accuracy can be improved. Further, since the shape of the magnet can be reduced, the shape of the angle sensor can be reduced. Further, in the hard magnetic material according to the present invention, the ratio (Ir / Is) of the residual magnetization (Ir) to the saturation magnetization (Is) is 0.6 or more, and the maximum magnetic energy ((BH) max) is increased. Therefore, the detection accuracy of the angle sensor can be greatly improved.

The angle sensor of the present invention has a remanent magnetization (Ir)
Is 90 emu / g or more and the coercive force is 2 kOe or more, so that the detection accuracy of the angle sensor can be greatly improved.

The hard magnetic material according to the present invention mainly contains a fine crystalline phase having an average crystal grain size of 100 nm or less.
m and a R ₂ Fe ₁₄ B phase having an average crystal grain size of 100 nm or less are precipitated, so that a soft magnetic phase (bcc (body-centered cubic structure) -Fe) and a hard magnetic phase (R
The exchange coupling characteristics of ₂ Fe ₁₄ B) are improved, and the remanent magnetization (Ir), squareness ratio (Rs), coercive force (iHc), and maximum magnetic energy product ((BH) max) are increased. Since hard magnetic characteristics are obtained, the detection accuracy of the angle sensor can be improved.

Further, the hard magnetic material used for the angle sensor of the present invention can obtain excellent hard magnetic properties even when the content of the rare earth element R is reduced, so that the Sm-Co based magnet or Nd-
The manufacturing cost can be reduced as compared with the angle sensor using the Fe-B based magnet. Further, the hard magnetic material used in the angle sensor described above is obtained by subjecting an alloy powder having an amorphous phase as a main phase obtained by quenching a molten alloy to heat treatment,
Since it is a consolidated body that is solidified and formed at the same time as crystallization, a magnet having a free shape can be easily manufactured. In addition, a hard magnetic material having excellent hard magnetic properties can be obtained by setting the conditions of the heat treatment such that the heating rate is 10 ° C./min or more, the heat treatment temperature is 600 to 800 ° C., and the holding time is 1 to 60 minutes. The detection accuracy of the angle sensor can be improved.

[Brief description of the drawings]

1A and 1B are diagrams showing a rotary encoder according to an embodiment of the present invention, wherein FIG. 1A is a perspective view showing a main part of the rotary encoder, and FIG. 1B is a perspective view showing a rotor of the rotary encoder. is there.

FIG. 2 is a cross-sectional view showing a main structure of an example of a spark plasma sintering apparatus according to an embodiment of the present invention.

3 is a diagram showing an example of a pulse current waveform applied to a raw material powder in the discharge plasma sintering apparatus shown in FIG.

FIG. 4 is a graph showing a demagnetization curve (second quadrant) of a thin strip alloy sample having a composition of Fe ₇₆ Co ₁₀ Nb ₂ Pr ₇ B ₅ at 302.5 K to 489 K;

FIG. 5 shows a demagnetization curve of a ribbon alloy sample having a composition of Fe ₆₆ Co ₂₀ Nb ₂ Pr ₇ B ₅ at 308 K to 471 K (second
4 is a graph showing a quadrant.

FIG. 6 is a graph showing a demagnetization curve (second quadrant) of a thin alloy sample having a composition of Fe ₈₄ Nb ₂ Pr ₇ B ₅ Si ₂ at 301.5K to 477K.

FIG. 7 is a diagram showing a relationship between magnetic properties and temperature of the thin strip alloy sample of the example and the magnet of the comparative example.

FIG. 8 is a diagram showing the temperature change of Ir when the ribbon alloy sample of the example and the magnet of the comparative example are used in a shape where p = 1.5 and p = 10, respectively.

FIG. 9 shows the permeance coefficient and temperature coefficient of a sintered bulk (alloy compact) within the composition range of the present invention, a ribbon alloy within the composition range of the present invention, and a conventional Nd—Fe—B magnet. FIG.

FIG. 10 is a graph showing a temperature change of magnetization of a hard magnetic material having a composition of Fe ₈₈ Nb ₂ Pr ₅ B ₅ and a hard magnetic material having a composition of Fe ₈₈ Pr ₇ B ₅ .

FIG. 11 is a graph showing the magnetization curves of the hard magnetic material having the composition Fe ₈₈ Nb ₂ Pr ₅ B ₅ and the hard magnetic material having the composition Fe ₈₈ Pr ₇ B ₅ in the second quadrant.

FIG. 12 is a graph showing a relationship between an operating temperature and an output voltage of the rotary encoder according to the embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 11 rotary encoder 12 motor 13 rotating shaft 14 rotor 15 magnet (consolidated magnet) 16 rotating drum 17 detecting unit

──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Hatanai, Inventor Takashi Hatani 1-7, Yukitani-Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Yutaka Yamamoto 1-7, Yukitani-Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Ichiro Tokunaga 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Mitsumasa 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Within Electric Co., Ltd. (72) Inventor Akihisa Inoue 35-81 Kawauchi Motoakura, Aoba-ku, Sendai City, Miyagi Prefecture Kawauchi House 11-806 (56) JP, A) JP-A-8-337839 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 7/30 101 H01F 1/053

Claims (5)

(57) [Claims] 1. A pressure formed of a hard magnetic material and solidified and formed.
Closely magnet, and a detector for detecting a change in magnetic flux from the compaction magnet, the hard magnetic material, Fe, Co, 1 or a more elements T of Ni, 1 kind of rare earth elements An alloy comprising the above elements R and B, having a permeance coefficient of 2
The absolute value of the temperature coefficient of magnetization when used in the above shape is 0.06 % / K in the temperature range from room temperature to 80 ° C.
And the ratio (Ir / Is) of the residual magnetization (Ir) to the saturation magnetization (Is) is 0.6 or more ,
An angle sensor comprising the following composition . T _x M _y R _z B _w However, T is Fe, Co, one or more elements of Ni
M represents one or more of Zr, Nb, Ta, and Hf.
R represents one or more rare earth elements
In addition, x, y, z, and w indicating the composition ratio are atomic%.
Where 86 ≦ x ≦ 92, 0.5 ≦ y ≦ 3, 3 ≦ z ≦ 7,3
≦ w ≦ 7. 2. The angle sensor according to claim 1, wherein
The hard magnetic material has a residual magnetization (Ir) of 90 emu / g.
An angle sensor having a coercive force of 2 kOe or more. 3. The angle sensor according to claim 1, wherein the hard magnetic material is obtained by heat-treating an alloy having an amorphous phase as a main phase obtained by rapidly cooling a molten alloy. An angle sensor comprising a fine crystalline phase having a particle size of 100 nm or less as a main phase. 4. The angle sensor according to claim 1, wherein the hard magnetic material is a powder of an alloy having an amorphous phase as a main phase obtained by quenching a molten alloy. An angle sensor characterized in that it is a compact that is solidified and formed simultaneously with crystallization by heat treatment. 5. The angle sensor according to claim 3, wherein a temperature rise rate during the heat treatment is 10 ° C./degree.
Min or more, the heat treatment temperature is 600 to 800 ° C.,
An angle sensor having a holding time of 1 to 60 minutes.