JP4862275B2 - Manufacturing method of back yoke for magnetic encoder - Google Patents

Description

The present invention relates to a method of manufacturing Bakkuyo click magnetic encoder.

  As a magnetic encoder, a magnetic generator that generates a magnetic field attached to a rotating body, a magnetic field detection element that is attached to a fixed body so as to face the magnetic generator through a gap, and a signal from the magnetic field detection element A magnetic encoder including a signal processing circuit for processing, wherein the magnetizing body is formed of a disk-shaped or rectangular parallelepiped permanent magnet disposed at an axial end of the rotating body, and the rotating body It is known that the magnetic field detection element is arranged in the axial direction with a gap in the axial direction (for example, Patent Document 1).

Further, in this type of magnetic encoder, it is known to use a back yoke made of a magnetic material in order to improve magnetic characteristics (for example, Patent Document 2 and Patent Document 3). A laminated steel plate made by laminating a plurality of steel plates obtained by punching electromagnetic steel plates or the like by press working is used.
JP 2000-65596 A JP-A-9-253896 JP 2000-87104 A

  As described above, in the back yoke using the laminated steel plate, since the magnetic flux in the lamination direction exists, the magnetic flux density is lowered due to the generation of eddy current, which is a problem in increasing the sensitivity of the magnetic encoder. .

  Therefore, the present invention is intended to solve the above problem, and by using a three-dimensionally insulated material, it is possible to prevent a decrease in magnetic flux density and to improve the sensitivity of the magnetic encoder. An object is to provide a back yoke for an encoder, a magnetic encoder, and a manufacturing method thereof.

According to the first aspect of the present invention, there is provided a magnetic generator that is attached to a rotating body and generates a magnetic field, and a magnetic field detecting element that is attached to a fixed body with one side facing the magnetic generator and having a gap between the generator. In a method for manufacturing a back yoke provided on the other side of the fixed body, a soft magnetic material powder having a particle size of 10 μm or more and 300 μm or less and having a surface insulated, and the soft magnetic material as a binder a mixture of 0.05% to 1.0% or less of the polyimide resin in a weight ratio relative to the powder was filled in a heated cavity of the molding die to form a lubricating layer on the wall surface, the soft magnetic material powder after compression molding, a manufacturing method you prepared by heat treatment for removing distortion caused at the time of curing and molding of the binder.

According to the configuration of the first aspect , the generation of eddy current can be suppressed for the magnetic flux in any direction in the back yoke, the magnetic flux density can be improved and uniform, and the magnetic flux according to the rotation of the magnet generator The density can be detected by the magnetic field detection element with high sensitivity, and a back yoke capable of improving the accuracy of the magnetic encoder can be manufactured.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below do not limit the contents of the present invention described in the claims. In addition, all of the configurations described below are not necessarily essential requirements of the present invention. In each embodiment, by adopting a new magnetic encoder, a magnetic encoder back yoke, and a manufacturing method thereof that are different from the conventional ones, a magnetic encoder, a magnetic encoder back yoke, and a manufacturing method that are not conventionally obtained are obtained. The magnetic encoder, the back yoke for the magnetic encoder, and the manufacturing method thereof will be described.
Reference example

A reference example of the present invention will be described below with reference to FIGS. First, the back yoke 101 of the present invention will be described. The back yoke 101 is formed in a ring shape in which a through hole 102 is formed in the shaft core. The back yoke 101 is subjected to surface insulation treatment on a soft magnetic material powder such as electromagnetic soft iron and silica steel that can be magnetized and demagnetized relatively easily, that is, the soft magnetic material powder 114. A soft magnetic material powder 114 is compression-molded, and as the surface insulation treatment, an electric insulation film (not shown) is provided on the surface of the soft magnetic material powder 114, and this insulation film comprises a phosphate treatment, a resin film An insulating layer of electricity, such as an oxide coating by a sol-gel method, passes through the lines of magnetic force, and also functions as a binder (binder) of the soft magnetic material powder 114.

  Next, a method for manufacturing the back yoke will be described. The molding die 118 includes a female die 120 having a through hole 119, a male upper punch 121 inserted into the through hole 119 from above, and a cylindrical core pin 122 inserted from below the through hole 119, respectively. And a ring-shaped lower punch 123. The core pin 122 is disposed on the axial center z ′ of the through hole 119, the upper surface 122 a is disposed on the substantially upper surface of the female die 20, and the lower punch 123 is disposed concentrically on the outer periphery of the core pin 22. At the same time, it is fitted in the through hole 119, and its upper surface 123a forms a bottom surface. The upper punch 121 is formed with a through hole 126 into which the core pin 122 is fitted.

  In manufacturing, the core pin 122 and the lower punch 123 are inserted in the through hole 119 in advance, and the soft magnetic material powder 114 subjected to the surface insulation treatment is dropped into the accommodating portion 128 that accommodates the raw material such as the through hole 119. Fill with. The soft magnetic material powder 114 subjected to the surface insulation treatment is mixed with a lubricant in order to improve the filling property and compressibility.

  Next, the back yoke 101 is formed by inserting the upper punch 121 into the through hole 119 with a predetermined pressure. After the compression molding is completed in this manner, the upper punch 121 is raised and the lower punch 123 is raised to extract the molded body (back yoke) from the through hole 119. This molded body (back yoke) is subjected to a heat treatment such as annealing at 200 to 600 ° C. for hardening of the insulating layer and removal of distortion generated during molding.

Next, an example of a magnetic encoder suitable for the present invention will be shown below. 3 to 5, reference numeral 1 denotes a rotating body, 2 denotes a permanent magnet as a magnet generator fixed to the rotating body 1 via a rotating shaft 11, and the material is a ferrite magnet, an Sm—Co magnet, Ne— It is formed by either one of Fe-B magnets or dispersion type composite magnets in which various magnets are bonded with a polymer material, and is unidirectionally magnetized perpendicularly to the rotating shaft 11 as indicated by the arrows in the figure. ing. Reference numeral 3 denotes a fixed body disposed via the permanent magnet 2 and the gap K, and one side of the fixed body 3 faces the permanent magnet 2, and 4 denotes the fixed body 3 at intervals of 90 degrees in the circumferential direction. 4 attached magnetic field detection elements, which are concentric with the rotation center of the rotating body, and are located at positions where two pairs of magnetic field detection elements that are 90 degrees apart from each other in mechanical angle are 180 degrees out of phase with each other Two pairs are provided. That is, the positional relationship between the four adjacent elements is that the A ₁ phase detection element 41 and the B ₁ phase detection element 42 and the A ₂ phase detection element 43 and the B ₂ phase detection element 44 are each displaced by 90 degrees in mechanical angle. The A ₁ phase detection element 41 and the A ₂ phase detection element 43 and the B ₁ phase detection element 42 and the B ₂ phase detection element 44 are each displaced by 180 degrees in mechanical angle. Further, the signal processing circuit 5 includes a differential amplifier 51 that outputs differential signals V _A of V _A1 and V _A2 , which are output signals of the A ₁ phase and the A ₂ phase, respectively, and B ₁ phase and B ₂ phase respectively. A differential amplifier 52 that outputs a differential signal VB of V _B1 and V _B2 that are output signals, and an angle detection circuit 53 that detects a rotation angle from the differential signals V _A and V _B are provided. Here, the absolute angle detection method includes all methods for detecting angle information from a sine wave and cosine wave, such as a phase tracking method, a multiplication method, a phase modulation method, and digital arithmetic processing. The back yoke 6 is provided on the other side of the fixed body 3.

Next, the operation will be described. In the magnetic encoder, the magnetic flux is detected by the magnetic field detection elements 41, 42, 43, and 44 of each phase of A ₁ , A ₂ , B ₁ , and B _{2 with} the above configuration. When the rotating body 1 rotates once, one detection element detects a sinusoidal magnetic flux density corresponding to the rotation angle position as shown in FIG. When the rotating body 1 sometimes rotates eccentrically, the detected magnetic flux density waveform is displaced according to the amount of eccentricity. However, since the A phase and the B phase take the differential between the A ₁ phase and the A ₂ phase and the B ₁ phase and the B ₂ phase, which are 180 degrees out of phase with each other, the eccentricity amount is canceled out, as shown in FIG. Two sine waves that are 90 degrees out of phase, that is, when the rotation angle is θ, waveforms of sin θ and cos θ are obtained, and processing is performed by the angle detection circuit 53 that inputs the A phase and the B phase. The rotation angle of the absolute position is detected. In this case, as described above, the back yoke 101 can have a magnetic flux density close to that of the iron in the back yoke 101, and a specific resistance value that is two to three orders of magnitude higher than that of a metal material. The magnetic flux density can be improved and made uniform.

When the amount of eccentricity of the rotating body is extremely small, detection signals having waveforms of sin θ and cos θ are obtained by the A phase detection element and the B phase detection element in which the magnetic field detection elements are fixed at 90 ° intervals in the circumferential direction. May be. Further, the magnetic field detection element does not necessarily need to be provided concentrically with the A-phase detection element and the B-phase detection element with respect to the rotation center of the rotating body, and sufficient resolution can be obtained by adjusting the amplitude of the detection signal. Is possible. Furthermore, the magnetic field detection element is provided with two A-phase and B-phase detection elements, and the phase is 90 degrees out of phase with each other. However, the present invention is not limited to this. The phase may be shifted with. Furthermore, in the above reference example , the case where the Hall effect element is used as the magnetic field detection element has been described. However, the same effect can be obtained even when the magnetoresistive element is used.

In this manner, the present reference example, a permanent magnet 2 serving as magnetism generation body for generating a magnetic field mounted on rotating rotary body 1, the gap K between the permanent magnet 2 together with the permanent magnet 2 on one side faces The back yoke 101 is provided on the other side of the fixed body 3 and is used in a magnetic encoder provided with the magnetic field detecting element 4 attached to the fixed body 3. Since the material powder is compression-molded, the generation of eddy current is suppressed for the magnetic flux in any direction in the back yoke 101 and the permanent magnet 2 can be improved and uniformized. Thus, the back yoke 101 that can detect the magnetic flux density corresponding to the rotation of the magnetic encoder with high sensitivity and improve the accuracy of the magnetic encoder can be provided.

In this manner, the present reference example, a permanent magnet 2 serving as magnetism generation body for generating a magnetic field mounted on rotating rotary body 1, the gap K between the permanent magnet 2 together with the permanent magnet 2 on one side faces In the magnetic encoder provided with the magnetic field detecting element 4 attached to the fixed body 3, a back yoke 101 is provided on the other side of the fixed body 3, and the back yoke 101 has a soft magnetic material powder 114 subjected to surface insulation treatment. Since it is formed by compression molding, the generation of eddy current can be suppressed with respect to the magnetic flux in any direction in the back yoke 101 and the magnetic flux density can be improved and uniformized. Magnetic field detection element 4 can detect magnetic flux density according to rotation with high sensitivity.

Also, in this manner, the present reference example, in the manufacturing method of the magnetic encoder back yokes, filled with a soft magnetic material powder 114 whose surface is insulated in the cavity serving accommodating portion 128 of the mold 118, the soft Since the magnetic material powder 114 is compression-molded and then subjected to heat treatment, the back yoke 101 can suppress the generation of eddy currents with respect to the magnetic flux in any direction in the back yoke, and improve and equalize the magnetic flux density. Thus, the magnetic flux density according to the rotation of the permanent magnet 2 can be detected by the magnetic field detection element 4 with high sensitivity, and the back yoke 101 that can improve the accuracy of the magnetic encoder can be provided.

Further, as described above, in this reference example , the magnetomotive member is constituted by the disk-shaped or rectangular parallelepiped permanent magnet 2 disposed at the axial end of the rotating body 1 and the shaft of the rotating body 1. Magnetized in one direction perpendicular to the direction, the magnetic field detecting element 4 is arranged axially with a gap K in the direction of the permanent magnet 2, and the magnetic field detecting element 4 is at the center of rotation of the rotating body 1. The two pairs of magnetic field detecting elements 41, 43, 42, 44, which are arranged concentrically with respect to each other and whose phases are 90 degrees out of phase with each other in the circumferential direction, are placed at positions where the phases are shifted 180 degrees from each other. The signal processing circuit 5 is provided with differential amplifiers 51 and 52 for processing differential signals between the magnetic field detection elements 41, 43, 42, and 44 facing each other, and the absolute position of the rotating body 1 is determined. Since the value is detected, the permanent magnet 2 having a very simple structure and two or two facing the permanent magnet 2 Since an accurate sine wave signal can be obtained simply by providing the four magnetic field detecting elements 41, 43, 42, and 44, a magnetic recording medium that is long in the axial direction can be provided as in the prior art, or the outer shape of the rotating body 1 can be provided. Compared with the case where undulations are provided or an elliptical magnetic recording medium is provided, there is an effect that a highly accurate magnetic encoder having a simple structure, low cost and extremely high resolution can be provided.

8 and 9 show the first embodiment of the present invention. The same reference numerals are given to the same parts as in the above-mentioned reference example, and detailed description thereof is omitted. In this example, the back yoke 101 is The magnetism and demagnetization can be made relatively easily, for example, soft magnetic material powder such as electromagnetic soft iron, silica steel, etc., that is, formed by integrally fixing the soft magnetic material powder 114 via the binder 115, On the surface of the soft magnetic material powder 114, an insulating film 116 through which magnetic lines of force pass is formed. As the binder 115, a polyimide resin which is a polymer having a molecular structure such as a thermally and chemically stable imide ring (heterocycle) or aromatic ring in the main chain is used. The soft magnetic material powder 114 has a particle size (maximum width) of 10 μm or more and 300 μm or less, and preferably 10 μm or more and 100 μm or less. This is because if the particle size (maximum width) of the soft magnetic material powder 114 is less than 10 μm, the soft magnetic characteristics are deteriorated. On the other hand, if the particle size (maximum width) is larger than 300 μm, sufficient resistivity cannot be obtained. This is because high frequency cannot be obtained.

  The polyimide resin is wholly aromatic polyimide, bismaleide-based polyimide, addition-type polyimide, or the like, and the addition amount thereof is 0.05% or more and 1.0% or less, preferably by weight with respect to the soft magnetic material powder 114. Is 0.1 or more and less than 0.5%. This is because if the polyimide resin is less than 0.05%, the specific resistance is not maintained, whereas if the polyimide resin exceeds 1.0%, the density is difficult to increase and the magnetic flux density and permeability are lowered.

  In manufacturing using warm forming, the core pin 122 and the lower punch 123 are inserted in the through hole 119 in advance, and the lubricating layer 129 is formed on the wall surface of the accommodating portion 128 that accommodates the raw material such as the through hole 119. . This is provided on the upper surface of the female mold 120, and an aqueous lubricating liquid is ejected from a jet port facing the through hole 119 and applied to the wall surface and the surface of the housing portion 128. The applied lubricating liquid is applied to the female mold 120. Moisture is evaporated by heat, and a lubricating layer 129 is formed on the surface of the upper surface 123 a and the outer peripheral surface of the core pin 122 in addition to the wall surface of the through hole 119. As the lubricating liquid, an aqueous solution of 1% sodium benzoate and 1% dipotassium hydrogen phosphate is used and sprayed onto the mold wall surface heated to 120 ° C., whereby the aqueous solution evaporates and crystals as the lubricating layer 129 are formed on the wall surface. An exit layer is formed.

  Thus, the soft magnetic material powder 114 with the insulating film 116 formed in the state where the lubricating layer 129 is formed on the wall surface or the like of the housing portion 128 and the binder such as 0.2% by weight addition-type polyimide resin. The mixture with the polyimide resin is dropped into the heated storage portion 128 and stored.

Next, similarly to the reference example , the back yoke 101 is formed by inserting the upper punch 121 into the through hole 119 with a predetermined pressure. After warm forming is completed in this way, the upper punch 121 is raised and the lower punch 123 is raised to extract the molded body (back yoke) from the through hole 119. This molded body (back yoke) is later subjected to heat treatment such as annealing at 200 to 400 ° C. as necessary to cure the binder and to remove strain generated during molding.

  The back yoke 101 has a magnetic flux density B10KA / m: 1.67 T and a specific resistance: 500 μΩm. On the other hand, the back yoke magnetic flux density B10KA / m by the sintered material was 1.57 T and the specific resistance was 1 to 1.5 μΩm. As a result, the back yoke 101 according to the present invention enables a magnetic flux density close to that of iron, has a specific resistance value that is two to three orders of magnitude higher than that of a metal material, and enables a high permeability even in an alternating magnetic field. Is.

In the present embodiment as this, corresponding to claim 1, the permanent magnet 2 serving as magnetism generation body for generating a magnetic field mounted on the rotating body 1, and the permanent magnet 2 with one side to the permanent magnet 2 are opposed In the method for manufacturing the back yoke 101 provided on the other side of the fixed body 3 , the particle size is 10 μm. As described above, a mixture of a soft magnetic material powder 114 having a surface insulation treatment of 300 μm or less and a polyimide resin having a weight ratio of 0.05% to 1.0% as a binder 115 with respect to the soft magnetic material powder 114 is applied to the wall surface. lubricating layer 129 filled in a molding die cavity serving accommodating portion 128 which is heated to form, this after the soft magnetic material powder 114 compression molded, heat treatment for strain relief which occurs during curing and molding of the binder Made with Because to that, the generation of eddy current is suppressed even for the magnetic flux in any direction in the back yoke 101 back yoke can be improved and uniformity of the magnetic flux density, the magnetic flux density corresponding to the rotation of the permanent magnet 2 Can be detected with high sensitivity, and the back yoke 101 can be provided that can improve the accuracy of the magnetic encoder.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention.

It is a perspective view of the back yoke which shows a reference example . It is a sectional view of a forming device same as the above. It is a perspective view of the principal part of a magnetic encoder same as the above. It is explanatory drawing which shows the signal processing circuit which processes each phase signal output from a magnetic field detection element same as the above. It is a front view of the principal part of a magnetic encoder same as the above. It is explanatory drawing which shows the output of one magnetic field detection element same as the above. It is explanatory drawing which shows the output of a signal processing circuit same as the above. It is sectional drawing of the principal part of the back yoke which shows Example 1 of this invention. It is sectional drawing of the principal part at the time of shaping | molding same as the above.

1 Rotating body 2 Permanent magnet (Magnet generator)
3 Fixed body 4 Magnetic field detection element 5 Signal processing circuit
11 Rotation axis
51 amplifier
52 amplifiers
53 Angle detection circuit
101 Back yoke
114 Soft magnetic powder
115 binder
116 Insulation film
117 Superplasticizer
118 Mold
128 Housing (cavity)
129 Lubrication layer K Air gap

Claims (1)

A magnetic encoder comprising a magnet generator that is attached to a rotating body and generates a magnetic field, and a magnetic field detecting element that is opposed to the magnet generator and that has a gap between the magnet generator and is attached to a fixed body. In the manufacturing method of the back yoke provided on the other side of the fixed body ,
Particle size 10μm or more, a mixture of 0.05% to 1.0% or less of the polyimide resin in a weight ratio with respect to the soft magnetic material powder as the soft magnetic material powder and a binder insulated treating the surface with 300μm or less, the wall surface the lubricating layer filling the formed heated cavity of the molding die, and thereafter the soft magnetic material powder was compression-molded, be produced by heat treatment for removing distortion caused at the time of curing and molding of the binder A method of manufacturing a back yoke for a magnetic encoder.

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