JP2009036728A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetostrictive torque sensor that reduces magnetic interference between magnetic cores, raises sensor sensitivity, and enables recognition of a direction in which torque is imparted. <P>SOLUTION: The torque sensor includes N (where N is an integer of ≥4) pieces of magnetic cores each having a pair of yoke edge portions and a yoke connected portion around which a coil has been wound. In each of the magnetic cores, the respective centers of the edge surfaces of the yoke edge portions are connected by a line forming a predetermined angle with the axial direction of a rotation axis to be detected by the torque sensor. The N magnetic cores are supported by insulating members so as to constitute a magnetic core unit. The N magnetic cores are arranged so that when the N magnetic cores are excited, adjacent magnetic cores have opposite magnetic flux components along the line connecting the respective centers of the edge surfaces of the yoke edge portions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a torque sensor that detects the axial torque of a rotating shaft in a non-contact manner using magnetostriction characteristics.

  For the power steering mechanism, engine control mechanism, power transmission mechanism, and the like of automobiles, a means for accurately detecting shaft torque has long been desired. By increasing the detection accuracy, precise control and efficiency can be improved, and various methods have been proposed so far. In particular, the method of detecting the shaft torque without contact using the magnetostrictive characteristics of the rotating shaft has a large overload capability, and is attracting attention as a method that replaces the conventional method of detecting the torque from the torsion amount of the torsion bar. .

  Various types of torque sensors of this type have been proposed, but all of them vary in permeability caused by torque, more specifically, + 45 ° and −45 ° with respect to the axial direction of the rotating shaft. The fluctuation of the magnetic permeability in the direction is detected by the detection coil. For example, in the technique disclosed in Patent Document 1, as shown in FIG. 25A, a magnetic film 503 having an inclination angle with respect to the axial direction is fixed to a rotating shaft 502 whose torque is to be detected. Excitation and detection are performed by the outer solenoid coil 504. However, since this method requires additional processing on the rotating shaft, there is a risk that reliability such as peeling of the magnetic film 503 may be impaired. Furthermore, since it is essential to specialize the shaft and increase the diameter, there is a problem that the mounting property is poor.

  For this reason, a torque sensor having a similar function without any processing on the rotating shaft has been proposed. For example, in the technique disclosed in Patent Document 2, a magnetic core is configured by attaching a large number of magnetic pieces having protrusions to a magnetic ring with magnetic pins, and a coil is wound around each magnetic pin to configure a torque sensor.

  Further, in Patent Document 3, a plurality of detection cores that form independent detection magnetic circuits between an excitation coil that is wound around the rotation axis in a non-contact manner and that excites the rotation axis in the axial direction, and the rotation axis. The detection core wheel is integrally formed by arranging the ring around the excitation region of the rotating shaft at equal intervals, and a magnetic detection unit that detects a magnetic field in each core that changes due to torque transmission. Yes.

JP-A-1-94230 JP-A-63-90730 Japanese Unexamined Patent Publication No. 62-249026

  However, there is still a problem to be overcome even with the improved technology of the patent literature.

  For example, in Patent Document 2, the magnetic ring is an integrated object, the cores adjacent in the circumferential direction are not separated, and noise is generated in the output due to magnetic interference. In this case, not only the sensitivity of the torque sensor is lowered, but also the direction of torque application cannot be identified. Moreover, since a coil is wound for each magnetic pin provided in large numbers, adjacent coils interfere with each other, and there is a limit to increasing the number of turns of the coil. Therefore, the output obtained is small and the sensitivity is low.

  Further, in the first embodiment of Patent Document 3, as in Patent Document 2 described above, since the magnetic ring is an integrated body, magnetic interference occurs at the adjacent detection core tip, and the sensitivity as a torque sensor is extremely high. It was low. Further, the exciting coil of the sensor was wound in a solenoid shape around the rotating shaft, and the detection core was arranged perpendicular to the axial direction of the rotating shaft. When torque is applied to the rotating shaft, the magnetic permeability changes at + 45 ° and −45 ° with respect to the axial direction of the shaft, but the sensor cannot be measured separately. That is, there is a problem that the direction of torque application cannot be identified.

  Furthermore, in the third embodiment of Patent Document 3, the magnetic rings are not used, and the detection U-shaped cores are independent from each other. However, the interval between adjacent cores is narrow, magnetic interference occurs between the cores, and the sensitivity is high. Declined. Also in this case, although the absolute value of the torque can be measured for the reason described above, the shape of the core is unsuitable as a torque sensor because the direction of torque application cannot be identified. In consideration of magnetic interference, even if one or two U-shaped cores are used, if a practical steel material with non-uniform magnetic properties on the shaft surface is used, the output voltage varies and torque can be measured accurately. could not. That is, the zero point fluctuation becomes large, which is not suitable as a torque sensor. Of course, in this case as well, the direction of torque application could not be identified.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique for reducing magnetic interference between magnetic cores, increasing the sensitivity of a sensor, and identifying the direction in which torque is applied. It is in.

The torque sensor of the present invention includes N magnetic cores having a pair of yoke end portions and a yoke connecting portion wound with a coil (N is an even number of 4 or more).
Each of the magnetic cores forms a predetermined angle with the axial direction of the rotating shaft to be detected by the torque sensor, wherein the line connecting the centers of the end surfaces of the yoke end portions is detected by the torque sensor,
The N magnetic cores are supported via an insulating member to constitute a magnetic core unit,
The magnetic cores are arranged so that when N magnetic cores are excited, magnetic flux components along a line connecting the centers of the end surfaces of the yoke end portions are opposite to each other in the adjacent magnetic cores. And
Here, the yoke end corresponds to the end face of the magnetic core functioning as a magnetic pole.

In the torque sensor of the present invention,
Adjacent magnetic cores have the opposite direction of winding the coil,
The N coils are connected in series, and coils of adjacent magnetic cores in a serial connection state are connected on different sides.

In the torque sensor of the present invention,
Adjacent magnetic cores have the same winding direction,
The N coils are connected in series, and coils of adjacent magnetic cores in series connection are connected on the same side.

  In any one of the torque sensors according to the present invention, it is preferable that the predetermined angle is set to approximately 45 °. Furthermore, a torque sensor is constituted by the first magnetic core unit in which the predetermined angle is set to about + 45 ° and the second magnetic core unit in which the predetermined angle is set to about −45 °. Is more preferable. About 45 ° ± 10 ° is allowed as about 45 ° (−about 45 ° corresponds to about −45 ° ± 10 °).

  The yoke connecting portion is a member that connects the yoke end portions in a magnetic circuit, and does not exclude the configuration of the thickness of the yoke connecting portion <the width of the yoke connecting portion in the axial direction of the rotating shaft. The outline of the cross section of the yoke connecting portion may be any of a polygon such as a circle, an ellipse, a rectangle, a rectangle, and a hexagon. However, in order to configure the yoke connection portion with a ferrite core produced by molding / sintering, a yoke end portion having a circular cross-sectional outline is preferable from the viewpoints of good moldability, suppressing chipping and good yield.

  In the torque sensor of the present invention, the yoke end portions can have the same shape. By sharing parts shapes, the number of manufacturing processes can be reduced, and mistakes in parts removal during assembly can be prevented.

In the torque sensor of the present invention,
It is desirable that the yoke end portion and the yoke connecting portion are made of Mn—Zn-based ferrite. Among the sintered cores of Mn—Zn ferrite, those having a high resistivity ρ can increase the efficiency of magnetic excitation and detection. Furthermore, when a material having particularly excellent high-frequency characteristics is used, the magnetic loss is low and the Curie temperature is high, so that it is easy to apply to automobile applications.

  N is an even number of 4 or more. For example, N is an even number within a range of 4 to 36. In the case of a machine tool device, the diameter of the rotating shaft may be increased, and it is desirable to increase N in order to suppress the zero point fluctuation when detecting the torque of the rotating shaft. When the diameter of the rotating shaft is limited to a certain range as in automotive applications, N is preferably any one of 4, 6 and 8 from the viewpoint of miniaturization and weight reduction.

  Specifically, the coil includes an excitation coil and a detection coil. In any of the coils, the excitation coil and the detection coil are preferably wound in the same direction.

  The insulating member that supports the N magnetic cores is preferably supported by an annular nonmagnetic member. The annular nonmagnetic member uses, for example, a resin that can be integrally molded, but can be replaced with another material (nonmagnetic organic material) as long as it can withstand an environmental temperature of about 80 ° C. As long as the yoke ends of the soft magnetic material are spaced at an arbitrary interval and the gap (magnetic gap) between the yoke ends and the surface of the rotating shaft is kept constant, the shape may not be a disk shape. However, a shaft hole for passing the rotation shaft is required at the center of the annular nonmagnetic member.

  The yoke end portion and the yoke connection portion may be fitted. In this case, it is preferable that a concave portion is provided in one of them, and the other has a convex portion that fits into the concave portion. The yoke end portion and the yoke connection portion may be bonded with an adhesive. The yoke end may be fitted with an annular nonmagnetic member (for example, a nonmagnetic ring). The yoke end and the annular non-magnetic member may be bonded with an adhesive.

  Further, the end surface of the yoke end on the shaft hole side may be a flat surface. However, it is preferable that the end surface of the yoke end on the shaft hole side is a curved surface that conforms to the shape of the surface of the opposing rotating shaft. If the distance between the curved end face (magnetic pole surface) and the rotating shaft is uniform when the axis of the rotating shaft is taken as a reference, the efficiency of magnetic excitation and detection can be improved. In other words, the magnetic gap between the yoke end and the rotating shaft is set to a dimension that does not interfere mechanically even if mechanical dimensional errors or rotational fluctuations occur during rotation. It is possible to reduce the magnetic resistance between the end portion of the yoke and the rotating shaft by making the surface facing the curved surface into a curved surface. Therefore, the magnetic flux can be applied from the magnetic core to the rotating shaft with a high magnetic flux density without increasing the number of turns of the coil and the current flowing through the coil. In addition, by making the surface of the yoke end facing the rotating shaft curved, it is possible to make the magnetic gap length between the yoke end and the rotating shaft uniform at each yoke end. The magnetic field applied to the rotating shaft is averaged, so-called excitation unevenness is suppressed, and the opposing area between the yoke end and the rotating shaft is large, so that the permeability change occurring on the surface of the rotating shaft can be detected efficiently. . That is, the zero point fluctuation can be reduced without particularly increasing the number of magnetic cores.

  In addition, it is preferable to provide a plurality of the magnetic cores and to dispose the magnetic cores magnetically apart from each other in order to suppress the zero point fluctuation.

  Moreover, it is good also as a structure which adds the exterior yoke part comprised with the material which can form a magnetic path, and is equipped with the said magnetic core unit magnetically isolate | separated from this exterior yoke part. Further, when the exterior yoke portion is cylindrical and the exterior yoke portion has an annular magnet, the N magnetic cores are accommodated in the exterior yoke portion.

  In addition, as materials for the yoke end portion and the yoke connection portion, Ni—Zn ferrite, iron powder, Fe-based amorphous (a laminate obtained by laminating or pulverizing and forming a ribbon is used as a yoke), Fe-based nanocrystalline material. (A yoke obtained by laminating or pulverizing and molding thin ribbons) can also be used.

  An excitation coil and a detection coil wound in an annular shape around the columnar yoke are included. Each of these coils can be constituted by winding a coil and hardening it with a resin, or winding a coil around a bobbin. The shape solidified with resin and the shape of the bobbin may be circular or rectangular. Further, the plate-like yoke may be provided with a shaking magnetic field superimposing coil wound in an annular shape in addition to the excitation coil and the detection coil. The shaking magnetic field superimposing coil may be wound in an annular shape so as to surround the periphery of the rotating shaft between the plate-like yoke and the rotating shaft surface. Here, the shaking magnetic field is a magnetic field applied to the shaft for the purpose of reducing the influence of pinning in the vicinity of the rotating shaft surface, which is one of the causes of hysteresis. The shaking magnetic field is obtained by applying an AC voltage having a frequency different from the excitation frequency to the exciting coil or the shaking magnetic field superimposing coil. In order to reduce the hysteresis, a technique for applying a special process such as attaching a magnetic film to the surface of the rotating shaft has been proposed, but the reliability of the rotating shaft is impaired. On the other hand, the superposition of the shaking magnetic field makes it possible to reduce the hysteresis in a non-contact manner with respect to the rotating shaft without performing special processing on the rotating shaft.

  According to the present invention, magnetic interference between magnetic cores can be suppressed. As a result, a high output can be obtained by the torque sensor, and the torque application direction can be identified.

  Next, the best mode for carrying out the present invention (hereinafter simply referred to as “embodiment”) will be specifically described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing the structure of the torque sensor 10 according to the first embodiment, and specifically, a cross-sectional view seen from a direction perpendicular to the axis of the rotating shaft 90. In the drawings shown below, reference numerals are omitted as appropriate in order to avoid complicated drawings and facilitate understanding.

  The torque sensor 10 detects torque applied to the rotating shaft 90 using magnetostriction characteristics. In order to use the magnetostriction characteristics as described above in the background art, the torque sensor 10 includes a first magnetic core unit 20 on the lower side of the figure that detects a change in permeability of + 45 ° with respect to the axial direction of the rotating shaft 90; And a second measurement unit 120 on the upper side of the figure for detecting a change in permeability of −45 °. By measuring the change in permeability in these two directions, the direction and magnitude of the torque applied to the rotating shaft 90 is detected. The rotating shaft 90 is formed of a magnetostrictive material, for example, nickel, chromium, molybdenum steel. This material is generally used, for example, as a crankshaft material in automobile engines.

  The entire first measurement unit 20 is accommodated in a general housing (not shown), and is fixed using, for example, a molding material (not shown). Further, the housing is provided with a lead-out portion, and an external circuit is provided therein. The external circuit supplies power to each coil, which will be described later, and acquires a detected output signal. Further, the housing is fixed by passing the fixing bolt through a fixing bolt hole provided around the housing and screwing it to an external fixing location. The second magnetic core unit 120 is also accommodated in the same housing. Hereinafter, the first magnetic core unit 20 will be described, and the description regarding the second magnetic core unit 120 will be omitted.

  FIG. 2 is a view showing the first magnetic core unit 20, FIG. 2 (a) is a plan view, FIG. 2 (b) is a cross-sectional view taken along line AA ′, and FIG. ) Shows a bottom view. FIG. 3 is a perspective view showing an appearance of the first magnetic core unit 20. FIG. 4 is a perspective view showing the appearance of one magnetic core unit. Here, one magnetic core unit is a unit composed of the first plate-like yoke 220a and the second plate-like yoke 220b (specific example of the yoke end) and the cylindrical yoke 240 (specific example of the yoke connecting portion). Point to. A bobbin 250 around which excitation coils 214a to 214d and detection coils 215a to 215d are wound is attached to each cylindrical yoke 240. Further, the cylindrical yoke 240 has a first plate-like yoke 220a attached to its lower end surface and a second plate-like yoke 220b attached to its upper end surface. The first plate-like yoke 220a and the second plate-like yoke 220b are parts having the same shape. A shaft hole 228 into which the rotating shaft 90 can be inserted is formed at the center of the first nonmagnetic ring 230a and the second nonmagnetic ring 230b. Note that the first magnetic core unit 20 includes four magnetic cores.

  FIGS. 5A and 5B are perspective views of the first plate-like yoke 220a viewed from the top and bottom surfaces, respectively. FIG. 6 is a perspective view when the four first plate-like yokes 220a are attached to the first nonmagnetic ring 230a. FIG. 4A is a perspective view seen from the top surface of the plate-like yoke, and FIG. 4B is a perspective view seen from the bottom surface of the first nonmagnetic ring. The first plate-like yokes 220a are arranged in the circumferential direction at equiangular intervals as viewed from the center of the shaft hole of the first nonmagnetic ring 230a (positions of 0 °, 90 °, 180 °, 270 °), and the first nonmagnetic yoke 220a. It is attached to the ring 230a. The nonmagnetic ring and the plate-like yoke are provided with holes 270 at predetermined positions. These are a cylindrical yoke 240 having a hole, a bobbin 250 around which an excitation coil and a detection coil are wound, a second plate-shaped yoke 220b, and a second nonmagnetic ring 230b, and the positions of the holes are aligned with bolts and nuts. Used for fastening. Although not shown, the second plate-like yoke 220b is similarly attached to the second nonmagnetic ring 230b.

  By providing the nonmagnetic rings 230a and 230b with convex portions 231a at predetermined positions, plate-like yokes can be attached at equal intervals. When the shaft is inserted into the magnetic core unit 20, the first and second plate-like yokes mounted at equal intervals respectively have the same size of the gap (magnetic gap) between the end surface on the shaft hole side and the surface of the rotating shaft. . Here, the end surface on the shaft hole side of the plate-like yoke facing the surface of the rotation shaft has a curved surface along the shape of the surface of the rotation shaft. The curved surface (magnetic pole surface) of the first plate-like yoke 220a facing the rotating shaft surface is 260a, and this curved surface (magnetic pole surface) of the second plate-like yoke is 260b.

  FIG. 7 shows FIG. 6 in a plan view and a cross-sectional view. 7A is a plan view, FIG. 7B is a cross-sectional view of A-A ′, and FIG. 7C is a bottom view. In the figure, a part of the nonmagnetic ring is not shown. The surface of the first plate-like yoke 220a that is formed low (thinner thickness is thin) is called a yoke connection portion 221, and the outer periphery is a part of a ring shape having a diameter R11 and a height h1. The height h1 is based on the bottom surface 224 of the yoke connection portion 221, and the following height h2 is the same.

  The convex portion 223 formed higher than the yoke connection portion 221 in the first plate-like yoke 220a faces the shaft surface of the rotating shaft through a gap (magnetic gap), and changes in magnetic permeability caused by excitation and torque application of the rotating shaft. It greatly contributes to detection. 223 has the same shape as a part of the ring having an outer diameter of R12 and an inner diameter of R13, and is formed to have a height h2. Therefore, a step having a height h2-h1 is formed between the yoke connecting portion 221 and the convex portion 223. The second plate-like yoke 220b has the same shape as the first plate-like yoke 220a as described above.

  As the material of the first and second plate-like yokes 220a and 220b, as the ferrite, Mn—Zn ferrite and Ni—Zn ferrite are preferable. In addition, as the powder, pure iron powder, Fe-Al-Si based sendust powder, Fe-based amorphous material, amorphous metal powder such as Fe-based nanocrystalline material, etc. are preferable, and the particle size of these materials is 200 μm or less. preferable. Further, as the nonmagnetic material used for the nonmagnetic ring, a resin, a Cu—Zn alloy such as brass, an Al—Si alloy, or the like, which hardly causes thermal deformation at about 80 ° C., is preferable. When a Cu—Zn alloy such as brass or an Al—Si alloy is formed by press working, the particle size of these materials is preferably 200 μm or less. Further, when the soft magnetic body (plate yoke or cylindrical yoke) and the nonmagnetic ring are made of the above-described powder material, they are separately formed as temporary molded bodies, and the first and second plate yokes 220a and 220b are formed separately. And a non-magnetic part are combined and formed into a ring shape by high-pressure molding (hereinafter, this molding method is referred to as two-color molding). A thermoplastic resin having an average particle size of 100 μm or less can be used as the binder in consideration of dispersibility in each material powder. The cylindrical yoke 240 may be the same as the material and forming procedure for the first and second plate-like yokes 220a and 220b.

  Next, the assembly procedure of the magnetic core unit 20 will be briefly described. FIG. 8 is a perspective view of the first and second nonmagnetic rings, the first and second plate-like yokes, the cylindrical yoke, and the bobbin constituting the magnetic core unit 20. As shown in the figure, the cylindrical yoke 240 is coupled so as to be placed on the first plate-like yoke 220a supported by the first nonmagnetic ring from above. Next, the cylindrical yoke 240 is inserted into the bobbin 250 around which the excitation coil and the detection coil are wound. Further, the second plate-shaped yoke 220b is coupled so as to cover the cylindrical yoke and the bobbin. At this time, the positions of the through holes 270 formed in the respective members are aligned, bolts are passed through the continuous through holes, and tightened with nuts.

  As a result, the first plate-like yoke 220a, the cylindrical yoke 240, and the second plate-like yoke 220b are joined, and as shown in FIG. 3, four pieces having the bobbin 250 around which the exciting coil and the detecting coil are wound. The magnetic core unit 20 including the magnetic core is completed. The nonmagnetic ring and the soft magnetic material included in the magnetic core unit 120 are mirror-symmetrical with those of the magnetic core unit 20, and the assembly procedure is the same.

  Since the nonmagnetic ring and the plate-like yoke form an annular portion, the assembly of the magnetic core unit is facilitated. The nonmagnetic ring has four convex portions, and the recess between adjacent convex portions is shaped to fit a plate-like yoke. Further, a groove having the same depth as that of the recess is formed between the convex portion and the peripheral edge of the nonmagnetic ring, so that the plate-like yoke can be easily fitted. Adjacent magnetic cores are magnetically separated by a non-magnetic ring. A magnetic core having a wide magnetic pole surface surrounds the rotating shaft closely, and the magnetic flux density distribution on the surface of the rotating shaft can be made substantially uniform.

  As in the prior art, it is difficult and time-consuming to wind a coil around the projecting magnetic pole on the inner periphery of the ring core. On the other hand, in the structure of FIG. 8, it is easy to insert a coil or a bobbin with a coil for each columnar yoke, and the man-hour can be shortened.

  In the configuration shown in FIG. 8, if one plate-like yoke and the cylindrical yoke are formed integrally in advance, a bobbin is inserted into the cylindrical yoke and combined with the other plate-like yoke to form one set of magnetism. A core can also be configured. Further, when one plate-like yoke and the cylindrical yoke are integrally formed in advance, the height of the cylindrical yoke is adjusted so that two plate-like yokes with a cylindrical yoke are combined to form a magnetic core. It is also possible.

  FIG. 9 schematically shows the positional relationship between the rotary shaft 90 and the end surfaces 260a, 260b facing the rotary shaft 90 of the first plate-like yoke 220a and the second plate-like yoke 220b in any one magnetic core. FIG. As shown in the figure, the line L1 connecting the centers of the two end faces 260a and 260b and the axial direction of the rotary shaft 90 form + 45 °. Although not shown, in the other magnetic cores in the magnetic core unit 20 as well, the end surface of the plate-shaped yoke facing the rotary shaft 90 is + 45 ° between the line connecting the centers and the axial direction of the rotary shaft 90. Eggplant. In the second magnetic core unit 120, the line connecting the centers of the end surfaces 260 a and 260 b facing the rotation shaft 90 and the axial direction of the rotation shaft 90 form −45 °.

FIG. 10 is a diagram showing circuit connections in the torque sensor 10, and FIG. 11 is a graph showing the relationship between torque and output voltage. The first output V _L1 detected by the first magnetic core unit 20 and the second output V _R1 detected by the second magnetic core unit 120 pass through the synchronous detection circuit 99a and are input to the operational amplifier 99b. As a result, a final output V _O1 is obtained. Note that the second output _{V R1} is the inverting input to the operational amplifier 99b. In the torque sensor 10, the magnetic core and the rotating shaft function like a magnetic core of a transformer in terms of electric circuit. Therefore, in FIG. 10, the magnetic core and the rotating shaft are represented by two thick lines.

  In FIG. 10, adjacent exciting coils are wound in opposite directions. The same applies to adjacent detection coils. Therefore, the winding directions of the exciting coil and the detecting coil wound around the same bobbin are the same. The coil 214a and the coil 214c are formed by winding a conductive wire so as to be clockwise when viewed in the plan view of FIG. In FIG. 2B, the coil 214b located on the front side of the paper surface is a wire wound in a counterclockwise direction when viewed in FIG. 2A. In FIG. 2B, the coil 214d positioned on the back side of the paper surface is a wire wound in a counterclockwise direction when viewed in FIG. 2A.

On the other hand, when adjacent exciting coils are wound in the same direction and adjacent detection coils are also wound in the same direction, the final output is V ₀₁ depending on the number of magnetic cores included in the magnetic core unit. May show different trends. For example, as shown in FIG. 2, when four magnetic core units (positions of 0 °, 90 °, 180 °, and 270 °) are included in one magnetic core unit, the interval between adjacent magnetic cores is narrow. Therefore, magnetic interference occurs, and the direction of torque application cannot be identified. For example, even if an attempt is made to detect a change in permeability that occurs in the + 45 ° direction, magnetic flux flows from the adjacent magnetic core. This flowing magnetic flux is a component in the −45 ° direction, and the final output V ₀₂ is the sum of V _L1 and V _R1 . As shown in FIG. 11, from V _02, although measurable absolute value of the torque, is applied the torque direction can not be identified.

  In addition, when the number of magnetic cores included in one magnetic core unit is two (positions of 0 ° and 180 ° or positions of 90 ° and 270 °), the distance between the first and second plate-shaped yokes, That is, since the distance between adjacent magnetic cores is sufficiently wider than the distance between 260a and 260b, magnetic interference between adjacent magnetic cores as described above is unlikely to occur. Therefore, even if the exciting coil and the detection coil are all wound in the same direction, the absolute value of the torque and the direction in which the torque is applied can be identified. When the number of magnetic cores in one magnetic core unit is one, the magnetic core that causes magnetic interference does not exist in the circumferential direction of the shaft, so naturally the absolute value of torque and the direction in which torque is applied are identified. it can. However, when the number of magnetic cores is one or two, the sensitivity is lower than when the number of magnetic cores is four, and hysteresis and zero point fluctuation are large. This is because the core area facing the shaft surface decreases with a decrease in the number of cores, and the contribution to excitation and detection decreases. In particular, when the number of magnetic cores is one, if the magnetic characteristics of the shaft surface are not uniform, the zero point fluctuation becomes extremely large, which is not suitable as a torque sensor. Therefore, using a large number of magnetic cores in which adjacent excitation coils and detection coils are wound in opposite directions has a higher output voltage, higher sensitivity, and smaller hysteresis and zero point fluctuations. It is.

  The AC voltage waveform applied to the exciting coil is a sine wave having a predetermined frequency and amplitude. At this time, an alternating voltage having a different amplitude from the predetermined frequency may be superimposed on the exciting coil. In addition, a superposition coil may be wound around each bobbin in order to superimpose the AC voltage. In this case, three coils for excitation, detection, and superposition are wound around one bobbin. The superimposing coil may be wound around the rotating shaft 90 around the outer periphery of the convex portion 223 of the first plate-like yoke 220a and the second plate-like yoke 220b.

Example 1
1 to 10, in this embodiment, in this embodiment, the excitation frequency is 20 kHz, the excitation current is 50 mA, the excitation coil is 100 turns, the detection coil is 200 turns, and the first and second plate-like yokes 220a and 220b are convex. The gap g (magnetic gap) between the portion 223 and the rotating shaft surface was set to 1 mm. A sintered body of Mn—Zn ferrite was used for the magnetic core. For the non-magnetic ring, a bake plate in which a fibrous material was hardened was used. The rotary shaft was nickel-chromium-molybdenum steel steel with φ18 mm subjected to induction hardening, and a torque of ± 140 Nm was applied. In this example, the sensitivity S was 1.0 mV / Nm, the hysteresis ε was 0.27%, and the zero point variation η was 0.9%. FIG. 12 shows the sensitivity S, hysteresis ε, and zero point variation η of this example and the comparative example. The sensitivity, hysteresis, and zero point fluctuation were defined by the following mathematical formulas (Equations 1 to 3) in FIGS.

Here, T _m is the absolute value of the torque applied, V _s is the voltage difference between the output voltage when the output voltage and the minimum torque when maximum torque is applied has been applied, V _h is no torque is applied The output voltage difference V _k is the difference between the maximum value and the minimum value of the output voltage obtained by rotating the rotating shaft one turn without applying torque.

  FIG. 12A shows the characteristics of the torque sensor of Example 1 and Patent Documents 2 and 3 according to the present invention in a table. In Patent Document 2, since the magnetic ring is an integral object, even if the detection core is mounted at ± 45 ° with respect to the axial direction, magnetic interference occurs between adjacent detection core tips, the sensitivity is extremely low, and torque The direction of grant cannot be identified. Further, in the third embodiment of Patent Document 3, independent U-shaped cores for detection are used, but the mounting angle of the core is not + 45 ° or −45 ° with respect to the axial direction. The resulting permeability change cannot be measured separately at + 45 ° or -45 °. That is, the direction of torque application cannot be identified. On the other hand, in the first embodiment of the present invention, the magnetic core is mounted at ± 45 ° with respect to the axial direction without using an integral magnetic ring. Furthermore, the excitation coil and the detection coil in the adjacent magnetic cores are wound in opposite directions. Therefore, in the first embodiment, the absolute torque value and the torque applying direction can be measured simultaneously.

FIG. 12B shows the number of magnetic cores and torque sensor performance in a table. When the sensitivity of Example 1 and each reference example are compared, Example 1 is the largest. In Reference Example 1, the excitation and detection coils of adjacent magnetic cores are wound in the same direction, and magnetic interference occurs between adjacent magnetic cores, and a signal corresponding to + 45 ° magnetic flux and a signal corresponding to −45 ° magnetic flux are generated. The components cannot be separated. In this case, the torque-output voltage characteristic shows the tendency of _V02 in FIG. On the other hand, in Example 1, the excitation and detection coils of adjacent magnetic cores are wound in the opposite direction, so that magnetic interference hardly occurs and high sensitivity is obtained. The sensitivity of 1.0 mV / Nm obtained here was sufficiently high, and a suitable result was obtained as a torque sensor used in the powertrain system of an automobile. On the other hand, Reference Examples 2 to 5 have fewer magnetic cores than Example 1. Under the same excitation conditions as in Example 1, the outputs of Reference Examples 2 to 5 are lower than those of Example 1, and the sensitivity is also lowered.

  Next, when the hysteresis of Example 1 and each reference example are compared, Example 1 has the lowest 0.3%. In Reference Examples 2 to 4, since the number of exciting cores is small, the surface of the rotating shaft cannot be sufficiently excited. Therefore, since the influence of pinning that causes hysteresis cannot be reduced, the hysteresis becomes a large value of 1.2 to 4.0%.

  Next, when the zero point fluctuations of Example 1 and Reference Examples 2 to 4 are compared, the zero point fluctuations of Reference Examples 2 to 4 are large. In Reference Examples 2 to 4, the number of magnetic cores is smaller than that in Example 1, and the total area of the bottom surface of the magnetic core facing the rotation shaft is small, so that it is difficult to uniformly excite the rotation shaft surface, and The area where signals can be detected is small. Therefore, when the magnetic characteristics of the shaft surface are not uniform, the output voltage varies periodically as the rotating shaft rotates, and the zero point variation tends to increase. On the other hand, the zero point fluctuation of Example 1 is 0.9%, which is a level that does not cause a problem in practical use of the torque sensor. In the first embodiment, four sets are provided in the magnetic core unit 20, and four sets are provided in the magnetic core unit 120. Therefore, signals from the shaft surface can be detected evenly, and even if the rotating shaft rotates, the fluctuation of the output voltage is small. From the above, when sensitivity, hysteresis, and zero point fluctuation are compared, Example 1 is suitable as a torque sensor.

(Direction of winding the exciting coil and magnetic flux component according to the embodiment)
FIGS. 15A and 15B are schematic diagrams for explaining the direction of winding the exciting coil and the direction of the magnetic flux component according to the first embodiment. FIG. 15A is a schematic diagram of a rotating shaft, FIG. ) And (d) are circuit diagrams each showing an example of circuit connection of the exciting coil. FIG. 15B is a diagram in which the surface (circumferential surface) of the rotating shaft in FIG. 15A is developed in a plane, and the dotted rectangular area shown on the rotating shaft surface 90f is the magnetic core in FIGS. This corresponds to a region facing the end face.

  More specifically, the end surfaces 260a and 260b of the first magnetic core plate-shaped yoke in FIGS. 3 and 4 are opposed to the regions S1 and N1 in FIG. 15B, respectively, and between S1 and N1. A magnetic flux in the direction indicated by the solid line arrow (thick line) flows on the rotation shaft surface 90f. The end surfaces 260a and 260b of the plate-shaped yoke of the second magnetic core face the regions S2 and N2 in FIG. 15B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S2 and N2. Flowed over the rotating shaft surface 90f. The end surfaces 260a and 260b of the third magnetic core plate-shaped yoke are opposed to the regions S3 and N3 in FIG. 15B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S3 and N3. Flowed over the rotating shaft surface 90f. The end surfaces 260a and 260b of the fourth yoke of the magnetic core face the regions S4 and N4 in FIG. 15B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S4 and N4. Flowed over the rotating shaft surface 90f.

  That is, in FIG. 15B, the direction of the magnetic flux flowing on the surface of the rotating shaft by the pair of end surfaces of the magnetic core is opposite in the adjacent magnetic core. In order to realize such a direction of the magnetic flux, when the magnetic core is arranged on the surface of the rotating shaft in (b), each magnetic core has a circuit connection as shown in FIG. 15 (c) or (d). Place and connect the excitation coil. The circuit connection in FIG. 15C is the same as that of the exciting coils 214a to 214d (on one magnetic core unit side) of the circuit in FIG. Therefore, the configuration of the entire circuit of the torque sensor is the configuration shown in FIG. The portions of the exciting coils 214e to 214h in the circuit of FIG. 10 are also made the same as the circuit connection of FIG. However, if the direction of the magnetic flux in FIG. 15B is + approximately 45 °, the direction of the magnetic flux in the excitation coils 214e to 214h (the other magnetic core unit side) of the circuit of FIG. To do. In addition, when one magnetic core unit and the other magnetic core unit are arranged close to each other in the rotation axis direction, if the magnetic core end faces of the same polarity are arranged close to each other (N poles are brought close to each other and S poles are placed close to each other) It is preferable because the magnetic flux leakage between the magnetic core units can be prevented.

First, in FIG. 15C, four exciting coils 214a, 214b, 214c, and 214d are connected in series, and the axis of each exciting coil faces the direction of the rotation axis.
In the first magnetic core, the exciting coil 214a is left-handed (the dotted arrow shown on the left side of the circuit diagram of the coil indicates that the coil is left-handed), and the current i is the axis of rotation. It flows along the direction parallel to the direction (the direction from the lower side to the upper side in FIG. 14). Then, a magnetic flux in the direction opposite to the rotation axis direction is excited at the yoke connection portion of the magnetic core around which the exciting coil 214a is wound (the solid arrow shown on the right side of the circuit diagram of the coil indicates the direction of the magnetic flux). The
In the second magnetic core, the exciting coil 214b is a right-handed winding (the chain line arrow shown on the left side of the circuit diagram of the coil indicates that the coil is a right-handed winding) and the current i is the rotation axis. It flows along the direction parallel to the direction. Then, a magnetic flux in the same direction as the rotation axis direction is excited at the yoke connecting portion of the magnetic core around which the exciting coil 214b is wound.
In the third magnetic core, the exciting coil 214c is left-handed and the current i flows along the direction parallel to the rotation axis direction. Then, a magnetic flux in the opposite direction (antiparallel direction) to the rotation axis direction is excited in the yoke connecting portion of the magnetic core around which the exciting coil 214c is wound.
In the fourth magnetic core, the exciting coil 214d is right-handed and the current i flows along a direction parallel to the rotation axis direction. Then, a magnetic flux in the same direction as the rotation axis is excited at the yoke connecting portion of the magnetic core around which the exciting coil 214d is wound.

Accordingly, when the current i is passed through the exciting coil in the direction shown in FIG. 15C (the terminal voltage of the circuit is in a relationship of V ₁ > V ₂ ), as shown in FIG. 15B. The end surface of the magnetic core facing the regions N1, N2, N3, and N4 is an N pole, and the end surface of the magnetic core facing the regions S1, S2, S3, and S4 is an S pole. That is, the magnetic flux components along the line connecting the centers of the end faces of the magnetic cores are opposite in the adjacent magnetic cores. However, when the direction of the current i shown in (c) is reversed (V ₁ <V ₂ ), the end face of the magnetic core facing the regions N1, N2, N3, and N4 becomes the S pole, and the regions S1, S2, The end face of the magnetic core facing S3 and S4 is an N pole.

  Regarding the direction of winding the coil, “right-handed winding” represents how to wind the coil of FIG. 19B, and “left-handed winding” represents how to wind the coil of FIG. 19C. In FIG. 15B, the width of the region (dotted square) is the plate shape shown in FIGS. 3 and 4 for easy understanding of the positional relationship with the exciting coil of FIG. 15C or FIG. It is shown smaller than the width of the end face of the yoke.

Next, a circuit connection (d) that can be used instead of FIG. 15 (c) will be described. In FIG. 15 (d), the four exciting coils 314a, 314b, 314c and 314d are connected in series, and the axis of each exciting coil faces the direction of the rotation axis.
In the first magnetic core, the exciting coil 314a is right-handed and the current i flows along the direction opposite to the rotation axis direction (anti-parallel direction). Then, a magnetic flux in the opposite direction (anti-parallel direction) to the rotation axis direction is excited in the yoke connecting portion of the magnetic core around which the exciting coil 314a is wound.
In the second magnetic core, the exciting coil 314b is right-handed, and the current i flows along a direction parallel to the rotation axis direction. Then, the magnetic flux in the same direction as the rotation axis direction is excited at the yoke connecting portion of the magnetic core around which the exciting coil 314b is wound.
In the third magnetic core, the exciting coil 314c is right-handed, and the current i flows in the direction opposite to the rotation axis direction (anti-parallel direction). Then, a magnetic flux in the opposite direction (antiparallel direction) to the rotation axis direction is excited in the yoke connecting portion of the magnetic core around which the exciting coil 314c is wound.
In the fourth magnetic core, the exciting coil 314d is right-handed and the current i flows along the direction parallel to the rotation axis direction. Then, a magnetic flux in the same direction as the rotation axis direction is excited at the yoke connecting portion of the magnetic core around which the exciting coil 314d is wound.

Therefore, when the current i flows through the exciting coil in the direction shown in FIG. 15D (the terminal voltage of the circuit is in a relationship of V ₁ > V ₂ ), as shown in FIG. 15B. The end surface of the magnetic core facing the regions N1, N2, N3, and N4 is an N pole, and the end surface of the magnetic core facing the regions S1, S2, S3, and S4 is an S pole. That is, the magnetic flux components along the line connecting the centers of the end faces of the magnetic cores are opposite in the adjacent magnetic cores.
When the torque sensor is configured by replacing the circuit of FIG. 15C with the circuit of FIG. 15D, the polarity of the coil is the same on the excitation side and the detection side, as shown in the circuit of FIG. It is good to. It is preferable to configure the excitation side and the detection side with the same polarity and arrangement because it is difficult to make mistakes in the parts during manufacture and the efficiency of assembly is good.

  FIG. 16 is a circuit diagram showing another example of circuit connection of the exciting coil. FIGS. 16A and 16B are examples of coil arrangements equivalent to those in FIG. 15C, in which the wiring connection is changed, and the exciting coils of adjacent magnetic cores in series connection are on the same side. (That is, they are connected at the coil ends on the root side of the arrow in the direction of the rotation axis). FIGS. 16C and 16D are examples of coil arrangements equivalent to those in FIG. 15D, in which the wiring connection is changed, and the exciting coils of adjacent magnetic cores in the serial connection state are on different sides. (That is, connected at the coil end on the tip side of the arrow in the direction of the rotation axis and at the coil end on the root side of the arrow). The display rules for the other circuit diagrams are the same as those in FIGS. 15C and 15D.

  FIG. 17 is a development view of the surface of the rotating shaft according to another embodiment, and (b) and (c) circuit diagrams showing circuit connections of the exciting coil, and the diameter of the rotating shaft in the form of FIG. Is equivalent to about 1.5 times and the number of magnetic cores is six. Although the number of magnetic cores is increased by two, it is the same as in FIG. 15 in that the magnetic flux components along the line connecting the centers of the end surfaces of the magnetic cores are reversed in the adjacent magnetic cores.

FIG. 18 is a circuit diagram showing another example of circuit connection of the exciting coil. 18 (a) and 18 (b) are examples of coil arrangements equivalent to those in FIGS. 17 (b) and 17 (d), respectively, in which the connection of wiring is changed, and for exciting magnetic cores in a series connection state. The coils are connected on different sides (that is, connected at the coil end on the tip side of the arrow in the direction of the rotation axis and the coil end on the root side of the arrow). When the number of magnetic cores is 6 or more, as shown in FIG. 18, “the coils of the magnetic cores in a series connection state are not connected to each other, but only connected by coils that are separated from each other, such as adjacent to each other. However, in order to efficiently assemble the magnetic core and the magnetic core unit shown in Fig. 3 and Fig. 4, as shown in Fig. 15 (d) and Fig. 17 (c), they are connected in series. It is suitable to connect the coils of adjacent magnetic cores on the same side in either manual assembly or automatic assembly because there is no waste in the assembly operation.
According to the magnetic core arrangement and the circuit arrangement according to FIGS. 15 to 18 described above, the magnetic flux components along the line connecting the centers of the end faces of the magnetic cores are opposite in the adjacent magnetic cores.

  19A is a schematic perspective view showing the direction of the magnetic flux in the magnetic core. FIG. 19B is a schematic perspective view showing the relationship between the direction of winding the exciting coil and the magnetic flux. In FIG. 19A, the magnetic core 30 is disposed so that a pair of end faces face the peripheral surface of the rotating shaft 90. An exciting coil 40 is wound around a central portion corresponding to the yoke connecting portion of the magnetic core 30. When the current i flows from one end a of the exciting coil and flows out from the other end b, magnetic flux is excited in the magnetic core 30 in the direction indicated by the solid line arrow (thick line), and a pair of end faces of the magnetic core In the vicinity of the surface of the rotation axis between the two, a magnetic flux inclined by about 45 ° with respect to the rotation axis direction is generated. When the direction of the current i is reversed, the magnetic core 30 is excited with a magnetic flux in the direction indicated by a one-dot chain line (thick line), and in the vicinity of the surface of the rotating shaft between the pair of end faces of the magnetic core, And a magnetic flux inclined about 45 ° is generated. In FIG. 19B, the exciting coil 40 is wound around the columnar core 60 with a right-handed screw. When a current i flows through the exciting coil 40 as shown in the drawing, the columnar core 60 is subjected to the so-called right-handed screw law. Magnetic flux φ is excited. In FIG. 19C, the exciting coil 50 is wound around the columnar core 60 by left-handed winding. When the current i is passed through the exciting coil 50 as shown, the illustrated magnetic flux φ is excited. The right-handed winding in FIG. 19B and the left-handed winding in FIG. 19C are in a mirror image symmetrical relationship.

(Direction of winding an exciting coil and direction of magnetic flux component according to another comparative embodiment)
FIG. 20 is a schematic diagram for explaining the direction of winding an exciting coil and the direction of a magnetic flux component according to another comparative embodiment, (a) a schematic diagram of a rotating shaft, (b) a developed view of the surface of the rotating shaft, (c) ) And (d) are circuit diagrams each showing an example of circuit connection of the exciting coil. FIG. 15B is a diagram in which the surface (circumferential surface) of the rotating shaft of FIG. 15A is developed in a plane, and the dotted square area shown on the rotating shaft surface 90f is the magnetic core of FIGS. This corresponds to a region facing the end face of the.

  More specifically, the end surfaces 260a and 260b of the first magnetic core plate-shaped yoke in FIGS. 3 and 4 are opposed to the regions S21 and N21 in FIG. 20B, respectively, and between S21 and N21. A magnetic flux in the direction indicated by the solid line arrow (thick line) flows on the rotation shaft surface 90f. The end surfaces 260a and 260b of the plate-shaped yoke of the second magnetic core face the regions S22 and N22 in FIG. 20B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S22 and N22. Flowed over the rotating shaft surface 90f. The end surfaces 260a and 260b of the third magnetic core plate-shaped yoke face the regions S23 and N23 in FIG. 20B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S23 and N23. Flowed over the rotating shaft surface 90f. The end surfaces 260a and 260b of the plate-shaped yoke of the fourth magnetic core are opposed to the regions S24 and N24 in FIG. 20B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S24 and N24. Flowed over the rotating shaft surface 90f.

  However, when the flow of magnetic flux indicated by the solid line arrow in FIG. 20B is generated, a leakage magnetic flux is generated between the plate-like yoke end surfaces of adjacent magnetic cores. Specifically, the leakage magnetic flux in the direction indicated by the one-dot chain line arrow (bold line) flows between N21 and S22, between N22 and S23, between N23 and S24, and between N24 and S21. Magnetic interference occurs, resulting in a lower sensitivity of the torque sensor than in the embodiment of FIG. Therefore, as shown in FIG. 20B, when the magnetic flux components along the line connecting the centers of the end surfaces of the yoke end portions are in the same direction in the adjacent magnetic cores, magnetic interference occurs between the magnetic cores. In particular, when the width of the end face of the plate-like yoke (width in the circumferential direction of the rotation axis) is increased, the end faces that generate the leakage magnetic flux are closer to each other, and the value of the leakage magnetic flux is further increased.

  FIG. 21 is a schematic diagram for explaining the direction of winding an exciting coil and the direction of a magnetic flux component according to still another comparative embodiment. FIG. 21A is a developed view of the surface of the rotary shaft, and FIGS. It is the circuit diagram which showed the example of the circuit connection of the coil for excitation. FIG. 15B is a diagram in which the surface (circumferential surface) of the rotating shaft of FIG. 15A is developed in a plane, and the dotted square area shown on the rotating shaft surface 90f is the magnetic core of FIGS. This corresponds to a region facing the end face of the.

  More specifically, the end surfaces 260a and 260b of the first magnetic core plate-shaped yoke in FIGS. 3 and 4 oppose the regions S31 and N31 in FIG. 21A, respectively, and between S31 and N31. A magnetic flux in the direction indicated by the solid line arrow (thick line) flows on the rotation shaft surface 90f. The end surfaces 260a and 260b of the plate-shaped yoke of the second magnetic core face the regions S32 and N32 in FIG. 21B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S32 and N32. Flowed over the rotating shaft surface 90f. The end surfaces 260a and 260b of the third magnetic core plate-shaped yoke are respectively opposed to the regions S33 and N33 in FIG. 21B, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S33 and N33. Flowed over the rotating shaft surface 90f. The end surfaces 260a and 260b of the fourth yoke of the magnetic core are opposed to the regions S34 and N34 in FIG. 21B, respectively, and the magnetic flux in the direction indicated by the solid line arrow (thick line) is between S34 and N34. Flowed over the rotating shaft surface 90f. The difference from the comparative example of FIG. 20 is that the magnetic flux components along the line connecting the centers of the end surfaces of the yoke end portions are mixed in the same direction and the different direction. is there.

  However, when the flow of magnetic flux indicated by the solid line arrow in FIG. 21B is generated, leakage magnetic flux is generated between the plate-like yoke end surfaces of some adjacent magnetic cores. Specifically, the leakage magnetic flux in the direction indicated by a one-dot chain line arrow (thick line) flows between N31 and S32 and between S33 and N34, causing magnetic interference between the magnetic cores. As a result, FIG. The sensitivity of the torque sensor is lower than that of the embodiment. Therefore, as shown in FIG. 21B, when the magnetic flux components along the line connecting the centers of the end surfaces of the yoke end portions include the same direction portions in the adjacent magnetic cores, magnetic interference occurs between the magnetic cores. Produce.

  FIG. 22 shows the combination of the soft magnetic material used for the first plate-like yoke 220a, the second plate-like yoke 220b and the cylindrical yoke 240 with the non-magnetic material used for the non-magnetic rings 230a and 230b, and the output sensitivity. It is a table | surface which shows these relationships. Here, three types of combinations 1 to 3 are illustrated.

  In the combination 1, the first plate-like yoke 220a and the second plate-like yoke 220b are temporary molded bodies obtained by press-molding a mixed powder of iron powder and binder at a low pressure. The nonmagnetic rings 230a and 230b are temporary molded bodies obtained by press molding a mixed powder of brass powder and binder at a low pressure. By combining these two types of temporary formed bodies and press-molding them at a high pressure, the components shown in FIG. 6 can be produced without using an adhesive or screws.

  In the combination 2, the first plate-like yoke 220a, the second plate-like yoke 220b, and the cylindrical yoke 240 are sintered bodies (ferrite cores) obtained by molding and sintering ferrite powder. The nonmagnetic rings 230a and 230b are formed of a resin or the like, or a green compact obtained by press molding a mixed powder of brass powder and binder. Then, the soft magnetic sintered body and the non-magnetic body are assembled with an adhesive to obtain the component shown in FIG.

  In the combination 3, the first plate-like yoke 220a, the second plate-like yoke 220b, and the cylindrical yoke 240 are green compacts obtained by press-molding a mixed powder of iron powder and binder. The nonmagnetic rings 230a and 230b are green compacts obtained by press-molding a mixed powder of brass powder and binder. The soft magnetic sintered body and the non-magnetic green compact are assembled with an adhesive to form the first and second plate-like yokes 220a and 220b and the cylindrical yoke 240. In this case, the nonmagnetic part may be a part made of a resin that can withstand an environmental temperature of 80 ° C.

  In any of the combinations 1 to 3, good sensitivity was obtained at the time of torque detection. However, particularly when the material of the combination 2 was used, the best sensitivity was obtained. In any combination, the pressing direction during molding is the same as the axial direction of the rotating shaft when the components are assembled.

  As described above, according to the first embodiment, the magnetic core unit is configured by three elements, and the assembly thereof can be facilitated. In addition, the magnetic core unit including the first and second plate-like yokes, the cylindrical yoke, and the bobbin has a ring shape, and can be easily mounted only by inserting the rotating shaft. That is, handling becomes easy, and an operation for making the dimensional accuracy of the gap (magnetic gap) between the surface of the rotating shaft and the magnetic poles proper becomes easy. In addition, a stable output voltage can be obtained by a plurality of magnetic cores arranged in the circumferential direction of the rotation axis. More specifically, the zero point fluctuation and the hysteresis are improved, and a countermeasure against shaft shake is facilitated.

(Second Embodiment)
FIG. 23 is a plan view showing a part of a representative shape of the first plate-like yoke that can be used in the magnetic core unit 20. FIG. 23A shows the first plate-like yoke 220a used in the first embodiment. The first plate yoke and the second plate yoke of the present invention can be attached to the bobbin 250 and the cylindrical yoke 240 having predetermined dimensions, and the first plate yoke 220a and the second plate yoke 220b. If the positional relationship between the end surfaces 260a and 260b facing the rotation shaft 90 and the rotation shaft 90 is the same as that in FIG. 9, the first plate-like yoke has the shape shown in FIGS. Also good. The second plate-like yoke used in the magnetic core unit 20 has the same shape as that shown in FIG. The first and second plate-like yokes used in the magnetic core unit 120 are mirror image symmetrical with the shape shown in FIG. Specifically, the plate-like yoke 220a shown in FIG. 23A is inverted with the side connecting the edge portions 520c and 520d as an axis.

  For example, as shown in the plate-like yokes 320 to 325 of FIGS. 23B to 23G, 420a, 420d, 421a to 421d, compared to the edge portions 520a to 520d of the plate-like yoke of FIG. 422a, 422d, 423a to 423d, 424a, 425a, 425b, and 425c are rounded. By rounding the edge portion, when the soft magnetic material is pressed with a die, the biting of the raw material powder is reduced, and the mass productivity is improved.

  Further, FIG. 23A may be modified as shown in FIGS. As shown in FIG. 1, when a rotating shaft is inserted into the torque sensor 10 and a predetermined exciting current is passed through the exciting coil, the first and second plate-like yokes and the cylinders will not be affected if each soft magnetic material does not cause magnetic saturation. The vicinity of the joint with the yoke may be miniaturized as shown in FIGS. In particular, FIGS. 23 (f) and 23 (g) require less soft magnetic material than FIG. 23 (a), and thus are excellent in cost and can be reduced in size and weight. The first and second plate-shaped yokes shown in FIG. 23 may be assembled in the same manner as in the first embodiment of FIG. 8 to constitute a magnetic core and a magnetic core unit.

  As in the first embodiment, the first and second plate-shaped yokes shown in FIG. 23 are preferably made of Mn—Zn ferrite and Ni—Zn ferrite as ferrite. In addition, as the powder, pure iron powder, Fe-Al-Si-based sendust powder, amorphous metal powder such as Fe-based amorphous material or Fe-based nanocrystal material, etc. are preferable, and the particle size of these materials is preferably 200 μm or less.

  When using ferrite as a raw material, it may be produced by press working using a mold. Moreover, when using said powder raw material, you may produce a 1st and 2nd plate-shaped yoke and a nonmagnetic ring by two-color shaping | molding as mentioned above.

  When configuring the magnetic core unit, adjacent exciting coils are wound in opposite directions. At this time, adjacent detection coils are also wound in opposite directions. That is, the excitation coil and the detection coil are wound around the same bobbin in the same direction. Even when the first and second plate-shaped yokes shown in FIG. 23 are used, a magnetic circuit similar to that in FIG. 10 is configured.

  The AC voltage waveform applied to the exciting coil is a sine wave having a predetermined frequency and amplitude. At this time, an alternating voltage having a different amplitude from the predetermined frequency may be superimposed on the exciting coil. Further, a superimposing coil may be wound around each bobbin 250 to superimpose the AC voltage. Further, the superimposing coil may be wound around a portion corresponding to the outer peripheral side of the convex portion 223 in the first and second plate-shaped yokes.

  As mentioned above, according to 2nd Embodiment, the effect shown in Example 1 in 1st Embodiment is acquired. Further, the edge portions of the first and second plate-like yokes are rounded, and the vicinity of the joint portion with the cylindrical yoke is reduced in size so that mass productivity is better than that of the first embodiment, and the size and weight are reduced. A magnetic core and a magnetic core unit can be manufactured.

(Third embodiment)
In the present embodiment, a DC bias magnetic field is applied in order to improve the output and accuracy of the torque sensor 10 shown in the first embodiment. Note that the present invention can also be applied to the configuration shown in the second embodiment.

  FIG. 24 is a diagram showing a configuration of a bias adding unit 700 in which a cylindrical bias yoke 710 is added to the magnetic core unit 20 shown in the first embodiment as a base. Here, the magnetic core unit 20 shown in the first embodiment is referred to as an internal magnetic core unit 20a for convenience. An internal magnetic core unit 20a is disposed inside a cylindrical bias yoke 710 via first and second spacers 746a and 746b. Hereinafter, this configuration is referred to as a bias addition unit 700. This figure shows a vertical cross-sectional view of the bias applying unit 700, and the right half of the drawing shows hatched portions that become magnetic paths.

  The bias yoke 710 includes a cylindrical bias yoke connection portion 758b, an annular upper yoke end portion 758a that fits in the opening of the bias yoke connection portion 758b, and an opening on the lower side of FIG. 24 of the bias yoke connection portion 758b. An annular lower yoke end portion 758c to be fitted, and a fixing plate 756c provided under the lower yoke end portion 758c. An annular first spacer 746a having a shaft hole 729a into which a rotation shaft is inserted at the center is disposed on the upper surface of the internal magnetic core unit 20a disposed on the bias yoke 710. In addition, an annular second spacer 746b having a shaft hole 729b into which the rotation shaft is inserted at the center is disposed on the lower surface of the internal magnetic core unit 20a. The shaft hole 729b has the same size as the diameter of the shaft hole formed in the center of the internal magnetic core unit 20a. The first and second spacers 746a and 746b are formed of a material capable of magnetically separating the bias applying unit 700 and the internal magnetic core unit 20a, and prevent magnetic interference.

  An opening 726a is formed in the central portion of the lower yoke end 758c, and a permanent magnet ring magnet 728 is fitted into the opening 726. A shaft hole 729b having a predetermined size is formed in the center portion of the ring magnet 728. The ring magnet 728 is sandwiched and supported by two members, a second spacer 746b and a fixing plate 756c provided below the second spacer 746b. Further, a cylindrical member 790 having a bias coil 769 wound around a bobbin is attached to the upper surface of the upper yoke connecting portion 758a. Specifically, a cylindrical third spacer 768b having upper and lower openings, an annular fixing plate 768a that closes the upper opening of the third spacer 768b, and an annular second opening that closes the lower opening of the third spacer 768b. 4 spacers 768c. The fourth spacer 768c magnetically separates the coil 769 and the upper yoke end 758a.

  A shaft hole for inserting the rotation shaft 90 is formed at the center of the fixed plate 768a and the fourth spacer 768c. These shaft holes are the same as the diameter of the central shaft hole of the internal magnetic core unit 20a. The cylindrical member 790 is formed with a through hole 745a. The through holes 745a, 270, and 745b of the internal magnetic core unit 20a, the bias yoke 710, and the cylindrical member 790 are connected to each other to form a set of through holes. Form holes. Thereby, the internal magnetic core unit 20a, the bias yoke 710, and the cylindrical member 790 can be fixed together with a bolt or the like.

  With the configuration as described above, by adding the ring-shaped bias yoke 710 having the ring magnet 728 to the internal magnetic core unit 20a, the bias magnetic flux is uniformly distributed in the circumferential direction. The influence of noise can be eliminated and torque detection accuracy is improved. Further, the amount of bias magnetic flux can be easily adjusted by changing the amount of current flowing through the bias coil 769. By using the ring magnet 728 and the bias coil 769 in combination, the power consumption can be suppressed as compared with the case where the bias magnetic flux is generated only by the bias coil 769. Note that a ring magnet 728 and a bias coil 769 may be provided on both the upper yoke end 758a and the lower yoke end 758c. Further, only one of the ring magnet 728 and the bias coil 769 may be used.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements, and such modifications are also within the scope of the present invention.

  The present invention can be widely used for torque sensors that use magnetostriction characteristics.

It is a figure which shows the structure of the torque sensor which concerns on 1st Embodiment. It is the figure which showed the 1st magnetic core unit. It is a perspective view which shows the external appearance of a 1st magnetic core unit. It is a perspective view which shows the external appearance of a magnetic core. It is a perspective view which shows a 1st plate-shaped yoke. It is a perspective view which shows the state which attached the four 1st plate-shaped yokes to the nonmagnetic ring. It is the top view and sectional drawing which show the state which attached the four 1st plate-shaped yokes to the nonmagnetic ring. It is an assembly drawing of a 1st measurement unit. It is the figure which showed typically the positional relationship of the surface which opposes a rotating shaft of the 1st and 2nd plate-shaped yoke in a 1st magnetic core, and a rotating shaft. It is the circuit diagram which showed the circuit connection of the torque sensor. It is the graph which showed the relationship between the applied torque and detection output. (A) Table showing structural features of the torque sensor used in Example 1 and Comparative Example of the first embodiment, (b) Used in Example 1 and Reference Example of the first embodiment. It is the table | surface which showed the sensitivity, zero point fluctuation | variation, and hysteresis of a torque sensor. It is the graph which showed the output voltage characteristic of the torque sensor. It is the graph which showed the output voltage characteristic of the torque sensor. It is the circuit diagram which showed the circuit connection of (a) the schematic diagram of a rotating shaft which concerns on 1st Embodiment, (b) The developed view of the rotating shaft surface, (c) and (d) coil. (A)-(d) It is the circuit diagram which showed the circuit connection of the coil. It is the circuit diagram which showed the circuit connection of the (a) development view of the rotating shaft surface and (b) and (c) coil which concern on other embodiment. (A) And (b) It is the circuit diagram which showed the circuit connection of the coil. (A) The schematic perspective view which showed the direction of the magnetic flux in a magnetic core, (b) And (c) The schematic perspective view which shows the direction which winds a coil, and the relationship of a magnetic flux. It is the circuit diagram which showed the circuit connection of (a) the schematic diagram of a rotating shaft which concerns on another comparative form, (b) The developed view of the rotating shaft surface, (c) and (d) coil. It is the circuit diagram which showed the circuit connection of the (a) development view of the rotating shaft surface which concerns on another comparative form, (b) and (c) coil. It is the table | surface which showed the combination of the material used for a soft-magnetic part and a nonmagnetic part, and the relationship of an output sensitivity. It is the top view which showed the shape of the 1st and 2nd plate-shaped yoke which concerns on 2nd Embodiment. It is the figure which showed the structure of the bias addition unit which concerns on 3rd Embodiment. It is the schematic which shows the structure of the magnetostrictive torque sensor based on a prior art.

Explanation of symbols

10: Torque sensors 20, 120, 400: Magnetic core unit 20a: Internal magnetic core unit 30: Magnetic core 40: Right-handed excitation coil 50: Left-handed excitation coil 60: Columnar cores 90, 502: Rotation Shafts 90f, 190f: Rotating shaft surface 99a: Synchronous detection circuit 99b: Operational amplifiers 214a-h: Excitation coils 215a-h: Detection coil 220a: First plate yoke 220b: Second plate yoke 221: Plate yoke Yoke connecting portion 223: plate-shaped yoke convex portion 224: plate-shaped yoke bottom surface 228, 729a, 729b: shaft hole 230a: first nonmagnetic ring 230b: second nonmagnetic ring 231a: convex portion of the first nonmagnetic ring 240: Cylindrical yoke 250: Bobbin 260a: End surface 260b of the first plate-like yoke facing the rotation shaft surface: Opposing the rotation shaft surface End surfaces 270, 745a, 745b of the second plate-shaped yokes: through holes 314a-314d: exciting coils 320-325: plate-shaped yokes 414a-414f: exciting coils 420a-420d, 421a-421d, 422a-422d, 423a- 423d, 424a to 424d, 425a to 425d, 520a to 520d: edge portion of plate-like yoke 503: magnetic film 504: excitation / detection solenoid coil 505, 506: detection magnetic core 507, 508: excitation magnetic core 514a to 514f: Excitation coils 614a to 614f: Excitation coil 700: Bias applying unit 710: Bias yoke 714a to 714f: Excitation coil 726: Opening 728: Ring magnet 746a: First spacer 746b: Second spacer 756c: Fixed plate 758a :Up Yoke end portion 758b: Biasing yoke connection portion 758c: Lower yoke end portion 768a: Fixing plate 768b: Third spacer 768c: Fourth spacer 769: Biasing coil 790: Cylindrical members 814a to 814d: Excitation coils 914a to 914d : Excitation coils 1014a to 1014d: Excitation coils 1114a to 1114d: Excitation coils

Claims (5)

N magnetic cores having a pair of yoke ends and a yoke connecting part wound with a coil are provided (N is an even number of 4 or more).
Each of the magnetic cores forms a predetermined angle with the axial direction of the rotating shaft to be detected by the torque sensor, wherein the line connecting the centers of the end surfaces of the yoke end portions is detected by the torque sensor,
The N magnetic cores are supported via an insulating member to constitute a magnetic core unit,
The magnetic cores are arranged so that when N magnetic cores are excited, magnetic flux components along a line connecting the centers of the end surfaces of the yoke end portions are opposite to each other in the adjacent magnetic cores. Torque sensor. The torque sensor according to claim 1,
Adjacent magnetic cores have the opposite direction of winding the coil,
A torque sensor characterized in that N coils are connected in series, and coils of adjacent magnetic cores connected in series are connected on different sides. The torque sensor according to claim 1,
Adjacent magnetic cores have the same winding direction,
A torque sensor characterized in that N coils are connected in series, and coils of adjacent magnetic cores connected in series are connected on the same side. The torque sensor according to any one of claims 1 to 3,
The torque sensor, wherein the predetermined angle is set to about 45 °. The torque sensor according to any one of claims 1 to 3,
A torque sensor comprising: a first magnetic core unit in which the predetermined angle is set to about + 45 °; and a second magnetic core unit in which the predetermined angle is set to about −45 °. .

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