JP2010054237A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetostrictive torque sensor with a simple structure, which can identify a torque assignment direction while reducing the magnetic interference between magnetic cores and enhancing the sensor sensitivity. <P>SOLUTION: The torque sensor includes a plurality of magnetic cores each including two yoke end parts, one yoke central part, and a yoke connection part with a coil wound thereon, the yoke end parts being connected to both end sides of the yoke central part through the yoke connection parts. In each of the magnetic cores, a line mutually connecting the centers of magnetostrictive detection faces formed in the yoke end part and the yoke central part forms a predetermined angle with the axial direction of a rotating shaft to be detected by the torque sensor, and the plurality of the magnetic cores is supported through an insulating member to constitute a magnetic core unit. <P>COPYRIGHT: (C)2010,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. 23 (a), 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 thereof is a torque core having a simple structure, which reduces magnetic interference between the magnetic cores, increases the sensitivity of the sensor, and identifies the direction in which the torque is applied. It is in providing a torque core that makes it possible.

  The torque sensor of the present invention has two yoke end portions, one yoke central portion, and a yoke connecting portion around which a coil is wound, and the yoke connecting portion is connected to both ends of the yoke central portion via the yoke connecting portion. A plurality of magnetic cores to which end portions are connected are provided, and each of the magnetic cores is a rotation which a line connecting the end portions of the yoke and the center of the magnetostriction detection surface formed at the central portion of the yoke is detected by a torque sensor. A predetermined angle is formed with respect to the axial direction of the shaft, and the plurality of magnetic cores are supported via insulating members to constitute a magnetic core unit.

  In the torque sensor, a line connecting the centers of one of the yoke ends and the center of the magnetostriction detection surface formed at the yoke central portion is + 45 ° with respect to the axial direction of the rotating shaft to be detected by the torque sensor. The line connecting the other end of the yoke and the center of the magnetostriction detection surface formed at the center of the yoke is set to approximately 45 ° with respect to the axial direction of the rotating shaft to be detected by the torque sensor. Are preferred.

When the magnetic core is excited by the current flowing through the coil, the magnetic flux components along the line connecting the centers of the magnetostriction detection surfaces formed at the yoke end and the yoke center are reversed by the adjacent magnetic core. It is preferable to configure the magnetic core so as to be oriented.
The direction in which the adjacent magnetic cores are wound with the coils is reversed, and the coils of the adjacent magnetic cores connected in series are connected on different sides while being connected in series. Moreover, the direction which the adjacent magnetic core wound the coil is the same, and while connecting the said coil in series, the coil of the adjacent magnetic core in a serial connection state is connected on the same side is applicable.

  The coil includes a coil wound around a yoke connection portion between one of the yoke end portions and the yoke center portion, and a coil wound around a yoke connection portion between the other yoke end portion and the yoke center portion. However, it is preferable that they are electrically connected alternately.

  The predetermined angle is preferably set to approximately 45 °. 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 above torque sensor of the present invention, the yoke end portions can be formed in two sets of line symmetrical shapes and combined with the yoke central portion to constitute a magnetic core. By sharing parts shapes, the number of manufacturing processes can be reduced, and mistakes in parts removal during assembly can be prevented. The yoke end is preferably plate-shaped. Miniaturization can be achieved when the magnetic core unit is assembled. Further, the yoke central portion may be an integral structure in which the two sets of yoke connecting portions are bonded together.

  In the torque sensor of the present invention, it is preferable that the yoke end 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.

  The number N of magnetic cores is an even number of 4 or more. For example, N is preferably 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, and the yoke center portion and the yoke connection portion may be fitted. In this case, it is preferable that a concave portion is provided on one side, 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 (magnetostriction detection surface) on the shaft hole side of the yoke end portion and the yoke center portion may be flat. However, preferably, the magnetostriction detection surface is a curved surface along the shape of the opposing surface of the rotating shaft. If the distance between the curved magnetostrictive detection surface and the rotation axis is uniform when the axis of the rotation axis is taken as a reference, the efficiency of magnetic excitation and detection can be improved. In other words, the yoke end and the magnetic gap between the yoke center and the rotating shaft are set to dimensions that do not interfere mechanically even if mechanical dimensional errors or rotational fluctuations occur during rotation. By making the magnetostriction detection surface formed in the central part and the yoke central part into a curved surface, it becomes possible to reduce the magnetic resistance between the yoke end part, the yoke central part and the rotating shaft. 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 magnetostriction detection surfaces of the yoke end and the yoke central part curved, it becomes 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 uneven excitation is suppressed, and the yoke end, the central portion of the yoke and the rotating shaft have a large facing area, so that the magnetic permeability change occurring on the rotating shaft surface 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.

  In the yoke connection portion, an exciting coil and a detecting coil are wound in an annular shape. 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. Furthermore, in addition to the excitation coil and the detection coil, a shaking magnetic field superimposing coil wound in an annular shape may be provided at the yoke end. 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 yoke end 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.

  ADVANTAGE OF THE INVENTION According to this invention, although it is a simple structure, the torque sensor which can suppress the magnetic interference between magnetic cores can be provided. 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 illustrating a structure of a torque sensor 10 according to the first embodiment. FIG. 1A shows a view from above, and FIG. 2B shows a cross-sectional view along AA ′. 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 utilize the magnetostriction characteristics as described above in the background art, the torque sensor 10 has a lower side in the figure for detecting a variation in magnetic permeability of + 45 ° with respect to the axial direction of the rotating shaft 90, and a magnetic permeability of −45 °. It has a measurement unit on the upper side in the figure for detecting fluctuation. 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 yoke end is housed 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.

  FIG. 2 is a perspective view showing an appearance of the magnetic core unit 20. FIG. 3 is a perspective view for explaining one magnetic core unit. Here, one magnetic core unit is a plate-like yoke end 220a, a plate-like yoke end 220b (a specific example of the yoke end) made symmetrically with the plate-like yoke end 220a, and a plane of these two yoke ends. A unit composed of a yoke central portion that is in contact with each other and a cylindrical yoke connecting portion 240 (specific example of the yoke connecting portion) that is connected to the yoke end portion on both the upper and lower sides of the yoke central 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 yoke connection portion 240. 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. The magnetic core unit 20 is configured to include four magnetic cores.

  4A and 4B are perspective views of the first yoke end 220a viewed from the top and bottom surfaces, respectively. FIG. 5 is a perspective view when four plate-like yoke end portions 220a are attached to the first nonmagnetic ring 230a. FIG. 4A is a perspective view seen from the top surface of the yoke end, and FIG. 4B is a perspective view seen from the bottom surface of the first nonmagnetic ring. The yoke end portions 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 ring 230a. Attached to. A hole 270 is provided at a predetermined position in the nonmagnetic ring and the yoke end. These holes are aligned with the yoke connecting portion 240 having a hole, the bobbin 250 around which the exciting coil and the detecting coil are wound, the yoke central portion 220c, the other yoke connecting portion 220b, and the second nonmagnetic ring 230b. Used for fastening with bolts and nuts. Although not shown, the other yoke end 220b is similarly attached to the second nonmagnetic ring 230b. However, the shape is symmetrical to that shown in FIG.

  The nonmagnetic rings 230a and 230b can be provided with convex portions 231a at predetermined positions so that yoke end portions can be attached at equal intervals. When the shaft is inserted into the magnetic core unit 20, the gap between the end surface on the shaft hole side and the surface of the rotating shaft (magnetic gap) is the same for each yoke end and yoke central portion attached at equal intervals. Become. Here, the end surface on the shaft hole side (magnetostriction detection surface) of the yoke end facing the rotation shaft surface has a curved surface along the shape of the rotation shaft surface. The magnetostriction detection surface of the yoke end 220a is denoted by 260a, and the curved surface (magnetic pole surface) of the yoke end is denoted by 260b.

  FIG. 6 shows FIG. 5 in a plan view and a cross-sectional view. 6A is a plan view, FIG. 6B is a cross-sectional view of A-A ′, and FIG. 6C is a bottom view. In the figure, a part of the nonmagnetic ring is not shown. A surface formed low (thinner thickness) at the yoke end 220a is referred to as a yoke plate-shaped 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.

  A convex portion 223 formed higher than the yoke plate-like portion 221 at the yoke end 220a is opposed to the shaft surface of the rotating shaft through a gap (magnetic gap), and changes in permeability caused by excitation and torque application of the rotating shaft. Significantly 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 plate-like portion 221 and the convex portion 223. The second yoke end 220b has the same shape as the yoke end 220a as described above.

  As materials for the yoke end portions 220a and 220b and the yoke center portion, 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 (yoke end, yoke central part or cylindrical yoke) and the non-magnetic ring are made of the above-mentioned powder material, they are separately formed as temporary molded bodies, and the first and second yoke ends are formed. The parts 220a and 220b and the non-magnetic part are combined and subjected to main molding under high pressure to form a ring shape (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 yoke end portions 220a and 220b.

  FIG. 7 is a view for explaining the central portion of the yoke. The figure is written in an arrangement when combined with the yoke end of FIG. As shown in FIG. 7A, the central portion of the yoke is symmetrical to the yoke end portion of FIG. Further, the thickness of the plate-like portion 229 is formed to be thicker than the yoke plate-like portion 221 at the yoke end in FIG. The thickness of the plate-like portion 229 preferably has a thickness of two cups with respect to the yoke plate-like portion 221 at the yoke end in FIG. This is because both yoke end portions are installed on the upper and lower sides, and the magnetic flux from both is concentrated on the central portion of the yoke so that the magnetic flux can be easily passed by that amount. For the same reason, it is preferable that the area of the magnetostriction detection surface at the convex portion 225 serving as the magnetostriction detection surface is twice that of the central portion of the yoke. Further, the yoke central part is formed so as to be contrasted up and down as shown in FIG. 7B, and the yoke end part 220a is arranged on one side and the yoke end part 220b is arranged on the other side via the yoke connection part 240. Is done.

  Next, the assembly procedure of the magnetic core unit 20 will be briefly described. The cylindrical yoke 240 is coupled through the through hole 270 so as to be placed on the yoke end 220a supported by the first nonmagnetic ring. Next, the bobbin 250 around which the exciting coil and the detecting coil are wound is inserted into the cylindrical yoke connecting portion 240. Further, the yoke connecting portion is coupled through the through hole 280 so as to cover the yoke central portion. Further, a yoke connecting portion 240 is installed on the other side of the yoke central portion, and the yoke end portion 220b is coupled to the upper surface. At this time, the positions of the through holes 270 formed in the respective members can be aligned, bolts can be passed through the continuous through holes, and the nuts can be fastened with nuts.

  As a result, the yoke end 220a, the yoke connecting portion 240, the yoke center portion 220c, the yoke connecting portion 240, and the yoke end portion 220b are joined in this order, as shown in FIG. The magnetic core unit 20 including the four magnetic cores having the bobbin 250 wound around is completed.

  Since the non-magnetic ring and the yoke end constitute an annular portion, the assembly of the magnetic core unit is facilitated. The nonmagnetic ring is formed with four convex portions, and the recess between adjacent convex portions is shaped to fit the yoke end. Furthermore, a groove having the same depth as the recess is formed between the convex portion and the peripheral edge of the nonmagnetic ring, and the yoke end portion 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 this invention, it is easy to insert a coil or a bobbin with a coil for every columnar yoke connection part, and can reduce a man-hour.
If one yoke end and yoke connecting portion are formed integrally in advance, a bobbin can be inserted into the cylindrical yoke and combined with the yoke central portion to form a set of magnetic cores. Further, by adjusting the height of the yoke connecting portion, one yoke end and the yoke connecting portion are integrally molded in advance, the yoke connecting portion and the yoke central portion are integrally molded, and the two are combined to form a magnetic core. It is also possible to configure.

  FIG. 8 shows the positional relationship between the rotary shaft 90 and the end surfaces 260a, 260b, 260c facing the rotary shaft 90 of the yoke end 220a, yoke central portion 220c, and yoke end 220b in any one magnetic core. It is the figure shown typically. As shown in the figure, the line L1 connecting the centers of the two end faces 260b and 260c and the axial direction of the rotary shaft 90 form + 45 °. A line L2 connecting the centers of the two end surfaces 260c and 260a and the axial direction of the rotation shaft 90 form −45 °.

FIG. 9 is a diagram showing circuit connections in the torque sensor 10, and FIG. 10 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. 9, the magnetic core and the rotating shaft are represented by two thick lines.

  In FIG. 9, 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. 1B, the coil 214b positioned on the front side of the paper surface is a wire wound in a counterclockwise direction when viewed in FIG. 1A. In FIG. 1B, the coil 214d located on the rear side of the paper surface is a wire wound in a counterclockwise direction when viewed in FIG. 1A.

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. 1, 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, a magnetic flux flows from an 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. 10, from V ₀₂ , the absolute value of torque can be measured, but the direction of torque application cannot 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 yoke ends, 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 due to the decrease in the core area facing the shaft surface and the contribution to excitation and detection as the number of cores 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 rotation shaft 90 around the outer periphery of the yoke end 220a, the convex part 223 of the yoke end part 220b, and the convex part 225 of the central part of the yoke.

Example 1
In the torque sensor having the configuration shown in FIG. 1, 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, the convex portions 223 of the yoke end portions 220a and 220b, and the surface of the rotating shaft. The gap g (magnetic gap) was 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%. Sensitivity, hysteresis, and zero point fluctuation were defined by the following equations (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. 13 is a table showing the characteristics of the torque sensor of Example 1 and Patent Documents 2 and 3 according to the present invention. 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.

(Direction of winding the exciting coil and magnetic flux component according to the embodiment)
FIGS. 14A and 14B 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, and FIG. 14A is a schematic diagram of a rotating shaft, and FIG. (C) is a circuit diagram showing an example of circuit connection of the exciting coil. FIG. 14B is a diagram in which the surface (circumferential surface) of the rotating shaft of FIG. 14A is developed in a plane, and the dotted square area shown on the rotating shaft surface 90f is the magnetic core of FIG. 2 and FIG. This corresponds to a region facing the end face.

More specifically, in FIG. 3 and FIG. 4, the yoke end of the magnetic core and the end surfaces (magnetostriction detection surfaces) 260a, 260b, and 260c of the yoke center are opposed to the square region surrounded by the broken line in FIG. Arranged to do.
In the region number, “N” at the head indicates the position of the magnetostriction detection surface from which the magnetic flux generated by the exciting coil exits, and “S” indicates the position of the magnetostriction detection surface where the magnetic flux enters. It is. The second letters a, b, and c indicate the magnetostriction detection surfaces of the yoke end portions 220a and 220b and the yoke center portion 220c, and correspond to the alphabet of each yoke.
A magnetic flux in the direction indicated by the solid line arrow (thick line) flows on the rotation shaft surface 90f. In the leftmost magnetic core in FIG. 14B, the magnetic flux generated from the magnetostriction detection surface Nc1 at the center of the yoke flows toward the magnetostriction detection surfaces Sa1, Sb1 at the yoke ends on both sides. In the second magnetic core, the magnetic flux generated from both yoke end portions Na1 and Nb1 flows toward the magnetostriction detection surface Sc1 in the central portion of the yoke. Magnetic flux flows through the third and fourth magnetic cores in the same manner as the first and second magnetic cores.

  That is, in FIG. 14B, the direction of the magnetic flux flowing on the surface of the rotating shaft by the pair of magnetostriction detection surfaces of the magnetic core is opposite between adjacent magnetic cores. In order to realize such a direction of the magnetic flux, when the magnetic core is arranged on the surface of the rotating shaft of (b), the exciting coil of each magnetic core is arranged so as to be the circuit connection of FIG. Place and connect. The configuration of the entire circuit of the torque sensor is the configuration shown in FIG.

First, in FIG. 14C, four exciting coils 214a, 214b, 214c, and 214d are connected in series, and the axis of each exciting coil faces the rotation axis direction.
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.

Therefore, when the current i flows through the exciting coil in the direction shown in FIG. 14C (the terminal voltage of the circuit is in a relationship of V ₁ > V ₂ ), as shown in FIG. 14B. The end surface of the magnetic core facing each region with N at the head of the number becomes an N pole, and the end surface of the magnetic core facing each region with S at the head of the number becomes 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, if the direction of the current i shown in (c) is reversed (V ₁ <V ₂ ), the N pole and S pole of each region are reversed. It should be noted that not only the circuit connection of FIG. 14C but also other circuit connection methods can similarly set the N pole and the S pole in each region, and may be changed as appropriate.

FIG. 15 is a schematic diagram for explaining circuit connection of windings according to claim 4. Four yokes 240Ra, 240Rb, 240Rc, and 240Rd indicate yoke connecting portions installed between the yoke end portion 220b and the yoke center portion 220c of the magnetic core unit 20 (in the figure, a bobbin that actually winds windings). The four yokes 240La, 240Lb, 240Lc, and 240Ld are yoke connection portions installed between the yoke center portion 220c and the yoke end portion 220a.
Exciting coils 214a to 214d and detecting coils 215a to 215d are wound around the yoke connecting portions 240a to 250d, and exciting coils 214e to 214h and detecting coils 215e to 215h are wound around the bobbins 240e to 240h. Yes. Each coil is wired so as to alternately connect a yoke connection portion installed between the yoke end portion 220b and the yoke center portion 220c and a yoke connection portion installed between the yoke center portion 220c and the yoke end portion 220a. ing. In FIG. 15, exciting coils 214c, 214h, 214a, 214f and exciting coils 214d, 214g, 214b, 214e are connected. In addition, the detection coils 215c, 215h, 215a, and 215f are connected to the excitation coils 215d, 215g, 215b, and 215e. Since the offset voltage is improved by alternately connecting the coils to the yoke of one magnetic core unit and the other magnetic core unit in this way, the variation in the voltage applied to each yoke is reduced, and the torque sensor As a result, the sensitivity can be improved. The entire configuration of the torque sensor circuit is as shown in FIG.

  17, 18 and 19 show other examples of circuit connection relating to the fourth aspect. In FIG. 14, the positional relationship of the magnetostriction detection surfaces at the yoke end and the central portion of the yoke are all the same, but in FIGS. 18 and 19, two magnetic cores whose positional relationship is bilaterally symmetrical are arranged. The yoke end portion, the yoke center portion, the nonmagnetic ring, and the like are also changed to the shape associated therewith. If the magnetostriction detection surface is to be formed as wide as possible, it is preferable to use a magnetic core in which the positional relationship between the magnetostriction detection surfaces at the yoke end and the yoke center is the same as shown in FIGS. That is, all the same magnetic cores can be used.

  FIG. 20 shows a combination of a soft magnetic material used for the yoke end 220a, the yoke central portion 220c, the yoke end 220b and the yoke connecting portion 240 and a nonmagnetic material used for the nonmagnetic rings 230a and 230b. It is a table | surface which shows the relationship of a sensitivity. Here, three types of combinations 1 to 3 are illustrated.

  In the combination 1, the yoke end 220a, the yoke center 220c, the yoke end 220b, and the yoke connecting part are temporary molded bodies obtained by press-molding a mixed powder of iron powder and a 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. 5 can be produced without using an adhesive or screws.

  In the combination 2, the yoke end portion 220a, the yoke center portion 220c, the yoke end portion 220b, and the yoke connection portion 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 yoke end portion 220a, the yoke center portion 220c, the yoke end portion 220b, and the yoke connection portion 240 are green compacts obtained by press-molding a mixed powder of iron powder and a binder. The nonmagnetic rings 230a and 230b are green compacts obtained by press-molding a mixed powder of brass powder and binder. Then, the yoke end portions 220a and 220b, the yoke center portion 220c, and the yoke 240 connecting portion are formed by assembling the soft magnetic sintered body and the nonmagnetic green compact with an adhesive. 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 to be molded is the same as the axial direction of the rotating shaft when the components are assembled.

  As mentioned above, according to 1st Embodiment, a magnetic core unit can be comprised by 4 elements, and also the assembly can be made easy. Further, the magnetic core unit including the first and second yoke end portions, 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 hysteresis are improved, and countermeasures against shaft shake are facilitated.

(Second Embodiment)
21 and 22 are plan views showing a part of a typical shape of a yoke end that can be used in the magnetic core unit 20. In addition, if it sees as the shape of the projection figure of a plate-shaped part, a yoke center part can also be made into the same shape. FIG. 21A shows the yoke end 220a used in the first embodiment. The yoke end of the present invention can be attached to a bobbin 250 having a predetermined dimension and a cylindrical yoke 240, and the first yoke end may have a shape shown in FIGS. . The other yoke end used in the magnetic core unit 20 is mirror-symmetric with the shape shown in FIG. Specifically, the yoke end portion 220a in FIG. 21A is inverted with the side connecting the edge portions 520c and 520d as an axis.

  For example, as shown in yoke end portions 320 to 325 of FIGS. 21B to 21G, 420a, 420d, 421a to 421d, compared to the edge portions 520a to 520d of the yoke end portion 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.

  Moreover, you may deform | transform FIG. 21 (a) like FIG.21 (b)-(g). As shown in FIG. 1, when a rotary shaft is inserted into the torque sensor 10 and a predetermined exciting current is passed through the exciting coil, if each soft magnetic material does not cause magnetic saturation, the yoke end and the cylindrical yoke are joined. The part vicinity may be reduced in size as shown in FIGS. In particular, FIGS. 21 (f) and 21 (g) require less soft magnetic material than FIG. 21 (a), which is superior in cost and can be reduced in size and weight.

  As in the first embodiment, the first and second yoke end portions shown in FIG. 21 are preferably Mn—Zn based ferrite and Ni—Zn based 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 pressing using a mold. Moreover, when using said powder raw material, you may produce a 1st and 2nd yoke end part 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 yoke end portions shown in FIG. 21 are used, the same magnetic circuit as in FIG. 9 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 at the first and second yoke end portions.

  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 yoke end portions are rounded, and the vicinity of the joint portion with the cylindrical yoke is reduced in size so that the 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.

  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 the figure which showed the magnetic core unit of this invention. It is a perspective view which shows the external appearance of a 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 yoke end part. It is a perspective view which shows the state which attached the four yoke edge parts to the nonmagnetic ring. It is the top view and sectional drawing which show the state which attached the four yoke edge parts to the nonmagnetic ring. It is a top view of four yoke center parts. It is the figure which showed typically the positional relationship of the surface which opposes a rotating shaft of the 1st and 2nd yoke end part 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. 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. (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 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 torque sensor which concerns on other embodiment. It is the circuit diagram which showed the circuit connection of the other coil. It is the circuit diagram which showed the circuit connection of the other coil. It is the circuit diagram which showed the circuit connection of the other 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 yoke edge part which concerns on 2nd Embodiment. It is the top view which showed the shape of the 1st and 2nd yoke edge part which concerns on 2nd Embodiment. It is the schematic which shows the structure of the magnetostrictive torque sensor based on a prior art.

Explanation of symbols

10: Torque sensor 20: Magnetic core unit 90, 502: Rotating shaft 90f, 190f: Rotating shaft surface 99a: Synchronous detection circuit 99b: Operational amplifier 214a-h: Excitation coil 215a-h: Detection coil 220a, 220b: Yoke end Portion 220c: Yoke central portion 221: Yoke connecting portion 223 at the yoke end portion: Convex portion at the yoke end portion 224: Bottom surface of the yoke end portion 225: Convex portion at the yoke central portion 228: Shaft hole 230a: First nonmagnetic ring 230b : Second nonmagnetic ring 231a: convex portion 240 of first nonmagnetic ring: cylindrical yoke 250: bobbin 260a, 260b: magnetostriction detection surface 260c at the yoke end facing the surface of the rotating shaft: yoke facing the surface of the rotating shaft Magnetostrictive detection surfaces 270, 280 at the center: through holes 420a to 420d, 421a to 421d, 422a to 422d, 23a~423d, 424a~424d, 425a~425d, 520a~520d: yoke end of the edge portion 503: the magnetic film 504: excitation and detection solenoid coil 505, 506: detection for magnetic cores 507 and 508: exciting magnetic core

Claims (5)

A magnet having two yoke end portions, one yoke central portion, and a yoke connecting portion wound with a coil, and the yoke end portion is connected to both end sides of the yoke central portion via the yoke connecting portion. With multiple cores,
In each of the magnetic cores, a line connecting the centers of the magnetostriction detection surfaces formed at the yoke end portion and the yoke center portion forms a predetermined angle with the axial direction of the rotating shaft to be detected by the torque sensor,
A torque sensor characterized in that the plurality of magnetic cores are supported via an insulating member to constitute a magnetic core unit.   A line connecting the center of the magnetostriction detection surfaces formed at one yoke end and the yoke center is set to + 45 ° with respect to the axial direction of the rotating shaft to be detected by the torque sensor, and the other A line connecting the centers of the magnetostriction detection surfaces formed at the yoke end and the yoke center is set to approximately 45 ° with respect to the axial direction of the rotating shaft to be detected by the torque sensor. The torque sensor according to claim 1.   When the magnetic core is excited by the current flowing through the coil, the magnetic flux components along the line connecting the centers of the magnetostriction detection surfaces formed at the yoke end and the yoke center are reversed by the adjacent magnetic core. A torque sensor comprising the magnetic core so as to be oriented.   The coil includes a coil wound around a yoke connection portion between one of the yoke end portions and the yoke center portion, and a coil wound around a yoke connection portion between the other yoke end portion and the yoke center portion. The torque sensors according to claim 1, wherein the torque sensors are electrically connected alternately. The torque sensor according to any one of claims 1 to 4,
The torque sensor, wherein the predetermined angle is set to about 45 °.

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