JP6071609B2 - Magnetostrictive torque sensor - Google Patents

Description

  The present invention relates to a magnetostrictive torque sensor that detects torque based on a change in magnetic characteristics due to an inverse magnetostrictive effect. For example, when a vehicle is steered by an operation member such as a steering handle (steering wheel), the power of an electric motor is controlled by a steering system. The present invention relates to a magnetostrictive torque sensor suitable for application to an electric power steering device that transmits an auxiliary steering force (steering assist force) to a (steering system) and reduces an operation load on the operation member such as the steering handle by a driver.

  As shown in the schematic configuration diagram of FIG. 21, a pinion drive type electric power steering device 10 equipped with a magnetostrictive torque sensor (steering torque sensor) 44 according to the prior art is provided on a steering shaft (steering shaft) 14. The steering torque signal VT detected by the magnetostrictive torque sensor 44 shown in detail in FIG. 22 is converted into a steering torque signal VT3 (FIG. 23) by a conversion circuit provided in the ECU (control device) 110. Based on the steering torque signal VT3, the vehicle speed signal, and the motor rotation signal, the ECU 110 calculates a target motor current (target current) for generating power in the electric motor (motor) 36.

  The ECU 110 generates a drive voltage (PWM signal) for energizing the electric motor 36 with the target current, and detects an actual motor current energized in the electric motor 36 with a current sensor, and the target motor current and the actual motor are detected. Power is generated in the electric motor 36 by performing PI (proportional / integral) control so that the currents coincide.

  The power of the electric motor 36 is transmitted to the steering shaft 14 via a speed reduction mechanism 42 (worm gear 38 and worm wheel gear 40) provided on the pinion shaft 22 to reduce the driver's steering load (see Patent Document 1). ).

  Here, as the magnetostrictive torque sensor (steering torque sensor) 44, for example, a magnetostrictive torque sensor using NiFe plating as a magnetostrictive film mf (mf1, mf2) is used.

  FIG. 22 is a partial cross-sectional view of the pinion drive type electric power steering apparatus 10 using a conventional magnetostrictive torque sensor 44.

  FIG. 23 is a torque detection circuit diagram of a conventional magnetostrictive torque sensor 44.

  FIG. 24 is a characteristic diagram as an example of the output voltage VT [V] corresponding to the steering torque Ts [kgfcm] applied to the magnetostrictive torque sensor 44.

  As shown in FIGS. 21 and 22, the magnetostrictive film mf is provided with a first anisotropy ma1 and a second anisotropy ma2 having different directions above and below the pinion shaft 22, and a first detection is performed for each. A coil 51, a second detection coil 52, a third detection coil 53, and a fourth detection coil 54 are provided.

  As shown in FIG. 23, the first to fourth detection coils 51 to 54 are supplied with a DC power source Vbb through a resistor on one end side and connected to the output end of the switching element 68 on the other end side, and suppress peak values. Connected to a DC power supply Vbb through a resistor and a diode. The first to fourth detection coils 51 to 54 connected in this way are driven via the switching element 68 with a repetitive rectangular wave drive signal (excitation signal) Sd, and the first to fourth generations generated at this time are driven. The midpoint voltages Vma2 and Vma1 of the detection coils 51 to 54 are held by the bottom hold circuits 81 and 82, respectively, and then amplified by the amplifier circuits (also referred to as amplifiers) 83 and 84, and the output voltage VT1 shown by the characteristics of FIG. The output voltage VT2 is obtained.

  A steering torque signal VT3 (FIG. 24), which is a differential output between the output voltage VT1 and the output voltage VT2, is obtained by a differential amplifier circuit (also referred to as a differential amplifier) 86, and as described above, based on the steering torque signal VT3. The target current is calculated. Note that failure detection can be performed using the output voltages VT1 and VT2.

  In this case, by applying an alternating current based on the drive signal Sd to the first to fourth detection coils 51 to 54, a predetermined magnetic field is generated in the magnetostrictive film mf, and the output hysteresis is reduced.

  Note that the characteristic diagram of the torque detection circuit in FIG. 23 showing the relationship between the steering torque Ts and the output voltage VT in FIG. 24 has the same tendency although the inclination is different, so the characteristic diagram of the torque detection circuit according to the embodiment. Also used as.

  Next, Patent Document 2 proposes a torque detection device using a Hall element to detect the torque of a shaft (shaft) as in the present invention. The torque detection device according to Patent Document 2 is disposed near a shaft member that generates a twist corresponding to the magnitude of receiving torque, an amorphous member formed in a portion that receives the twist of the shaft member, and the amorphous member. A magnet having an S pole and an N pole, and a torque detecting Hall element that detects the magnitude of the torque based on a change in magnetic flux passing through the amorphous member in accordance with the magnitude of the torque. Two are provided at intervals, and are arranged so that the N pole of one magnet faces the S pole of the other magnet, and the S pole of the one magnet faces the N pole of the other magnet, The torque detecting Hall element is arranged at a substantially central position of the two magnets.

Japanese Patent Laying-Open No. 2006-64445 (FIG. 1) Japanese Patent Publication No.7-119657 (FIG. 1)

  The conventional magnetostrictive torque sensor 44 described with reference to FIG. 22 and the like uses the first to fourth detection coils 51 to 54 that are also used for excitation of multiple windings and uses the detection circuit shown in FIG. Thus, the steering torque can be detected with high sensitivity. However, since the four multiple winding first to fourth detection coils 51 to 54 are arranged to face each other, the magnetostrictive film mf is elongated in the axial direction. Further, since the number of turns of the first to fourth detection coils 51 to 54 is set to generate a predetermined magnetic field in the magnetostrictive film mf, the magnetostrictive torque sensor 44 is increased in size and weight. There was a problem.

  On the other hand, although the magnetostrictive torque sensor using the Hall element disclosed in Patent Document 2 is considered to be small and light in weight, the Hall element directly detects a change in magnetic flux generated by a permanent magnet. As a result, there is a problem that the robustness against external electromagnetic noise is low.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a magnetostrictive torque sensor that is small and lightweight and has improved robustness against external electromagnetic noise.

  In addition, in order to avoid duplication about the member which does not demonstrate the meaning of a code | symbol in said FIG. 21, FIG. 22, it demonstrates in the section of [Mode for carrying out the invention] (embodiment).

  A magnetostrictive torque sensor according to the present invention includes a shaft member, a magnetostrictive material having magnetic anisotropy provided in the shaft member, a field portion that outputs a magnetic flux that passes through the magnetostrictive material, and the field portion. A magnetostriction type comprising: a magnetic flux detection unit that detects the magnetic flux that is output and passes through the magnetostrictive material; and a torque detection unit that detects torque applied to the shaft member based on a detection result of the magnetic flux detection unit. In the torque sensor, the field portion includes a magnetic flux generation portion that generates a magnetic flux by a static magnetic field, and a yoke engaged with the magnetic flux generation portion, and the magnetic flux generated by the magnetic flux generation portion is The magnetic flux is outputted through a yoke, and the outputted magnetic flux is passed through the magnetostrictive material provided on the shaft material.

  According to the present invention, a magnetic flux generated by the static magnetic field generated by the magnetic flux generator is output via the yoke, the output magnetic flux is passed through the magnetostrictive material provided on the shaft member, and the magnetic flux passing through the magnetostrictive material is detected as a magnetic flux. Since the magnetic flux is passed through the yoke, the magnetic flux generated by the magnetic field portion can be detected by the magnetic flux detection portion through the magnetostrictive material with high efficiency (high magnetic flux density). it can. As a result, the detection accuracy (detection sensitivity) can be increased, and the robustness (toughness) against external electromagnetic noise is improved.

  For example, a permanent magnet or an electromagnet can be used as the magnetic flux generator that generates a static magnetic field that does not vary with time. The electromagnet may be configured such that a coil is wound around the yoke and a constant direct current is passed through the coil. As the magnetic flux detection unit, a magnetic sensor (magnetic flux detection device) such as a Hall element or a magnetoresistive element can be used. In addition, it is preferable to use a permanent magnet, and the power supply for a magnetic flux generation part becomes unnecessary.

  In this case, the yoke is formed to extend from the magnetic flux generating portion in both directions along the circumferential direction of the shaft member, and both open ends of the yoke extend from the yoke toward the shaft center of the shaft member, respectively. The teeth have a convex shape, and the magnetic flux is output from the magnetic flux generation unit through the yoke and one of the teeth, and the magnetic flux that has passed through the magnetostrictive material is input to the other tooth, and the magnetic flux is input to the yoke. The magnetic path is formed by returning to the magnetic flux generation section through the. The magnetic flux detection unit is provided in the magnetic path.

  The magnetic flux passing in the circumferential direction of the magnetostrictive material acts so as to exit from one tooth and enter the other tooth, so that the magnetic flux wraps around both sides of the magnetostrictive material in the circumferential direction. Therefore, even when the position of the yoke is displaced relative to the shaft center of the shaft material, the magnetic flux density at the tooth portion does not change, and the magnetic flux can be detected stably. In addition, since the magnetic flux passes through the entire circumference of the magnetostrictive film, the characteristics are averaged even if the film thickness of the magnetostrictive film is not uniform, and as a result, accurate torque can be detected. In this case, the said one tooth is arrange | positioned with respect to the said other tooth on the opposite side with respect to the axial center of the said shaft material.

  The yoke is formed in an arcuate shape, and the yoke formed in the arcuate shape has a center angle of less than 180 °, and an assembly including the field part and the magnetic flux detection part is formed as the shaft member. By providing them symmetrically with respect to the axial center, the detection sensitivity can be increased, and the magnetic flux can be detected more stably even when the yoke is displaced from the center of the shaft.

  In addition, the yoke extends from the magnetic flux generating portion along the circumferential direction of the shaft material to a position symmetrical to the shaft center of the shaft material in both directions, and further extends toward the shaft center. From the extended portion, it further branches and extends in both directions along the circumferential direction of the shaft member to form a plurality of branch yokes in the vicinity of the outer periphery of the shaft member, and the end portions of the branch yokes are opened. The open ends are respectively formed with teeth that are convex toward the shaft center of the shaft material, and are formed from the magnetic flux generating portion to one of the yokes, one of the branch yokes, and one of the respective ones. The magnetic flux is output through the teeth formed on the branch yoke, the magnetic flux passed through the magnetostrictive material is input to the teeth formed on the other branch yoke, and the other branch yoke is used. The other said A magnetic path is formed by passing the magnetic flux through the core and returning it to the magnetic flux generation section, and the magnetic flux detection section is provided in the magnetic path so that the shaft of the shaft member is orthogonal to the teeth. The detection accuracy can be maintained even if it is deviated.

  In this case, in the cross section orthogonal to the shaft center, the teeth are arranged in each of four regions formed by two lines orthogonal to each other through the shaft center. Even if the shaft is displaced in any direction, the detection accuracy can be reliably maintained.

  According to the present invention, it is possible to detect torque without using four multiplex winding excitation detection coils, and the magnetostrictive torque sensor can be reduced in size and weight.

  That is, the magnetic flux generated by the static magnetic field generated by the magnetic flux generator is output via the yoke, the output magnetic flux is passed through the magnetostrictive material provided on the shaft member, and the magnetic flux passing through the magnetostrictive material is detected by the magnetic flux detector. Because it is configured, it is possible to reduce the size and weight, and to pass the magnetic flux through the yoke, so that the magnetic flux generated by the field part can be detected by the magnetic flux detection part through the magnetostrictive material under high efficiency (high magnetic flux density). it can. As a result, detection accuracy (detection sensitivity) can be increased, and robustness (toughness) against external electromagnetic noise can be improved.

It is a typical block diagram of the pinion drive type electric power steering device carrying the magnetostrictive torque sensor which concerns on the 1st-4th Example of this invention. It is a typical block diagram of the column drive type electric power steering device carrying the magnetostrictive torque sensor which concerns on 1st-4th Example of this invention. It is front sectional drawing of the magnetostrictive torque sensor which concerns on 1st Example. FIG. 3 is a partially omitted perspective view of the magnetostrictive torque sensor according to the first embodiment. FIG. 3 is a schematic cross-sectional view of a main part of the magnetostrictive torque sensor according to the first embodiment, partly omitted. It is a partial omission perspective view of the principal part of the magnetostriction type torque sensor concerning the 1st example. It is a torque detection circuit diagram with which the magnetostrictive torque sensor which concerns on 1st Example and 2nd Example is provided. 8A and 8B are explanatory diagrams for providing magnetic anisotropy, respectively. It is a characteristic view which shows the relationship between input torque and relative magnetic permeability. It is a characteristic view which shows the relationship between input torque and the magnetic flux density of a yoke. FIG. 11A to FIG. 11C are schematic explanatory diagrams showing the correspondence between the magnetic permeability of the magnetostrictive film and the magnetic flux density. It is a partially-omission perspective view of the magnetostrictive torque sensor according to the second embodiment. FIG. 6 is a schematic cross-sectional view of a main part of a magnetostrictive torque sensor according to a second embodiment with a part omitted. It is a partial omission perspective view of the principal part of the magnetostriction type torque sensor concerning the 3rd example. FIG. 10 is a schematic cross-sectional view of a main part of a magnetostrictive torque sensor according to a fourth embodiment, partially omitted. It is a torque detection circuit diagram with which the magnetostrictive torque sensor which concerns on 4th Example is provided. FIG. 17A is an explanatory diagram of the flow of magnetic flux when the shaft and the center of the yoke constituting the magnetostrictive torque sensor according to the first embodiment are coincident, and FIG. 17B is the magnetostrictive torque according to the first embodiment. It is explanatory drawing of the flow of magnetic flux when the shaft material which comprises a sensor, and the center of a yoke have shifted | deviated. FIG. 18A is an explanatory diagram of the flow of magnetic flux when the yoke-side half circumference of the magnetostrictive torque sensor according to the first embodiment is a thick magnetostrictive film, and FIG. 18B shows the first embodiment. It is explanatory drawing of the flow of the magnetic flux in case the film thickness of the half circumference on the side which does not oppose the yoke which comprises the magnetostrictive torque sensor which concerns is a thick magnetostriction film | membrane. It is characteristic explanatory drawing which shows the relationship between the BH curve of a magnetostrictive film, and a bias magnetic field. It is characteristic explanatory drawing which shows the relationship between the magnetic field and magnetic permeability of a magnetostrictive film. It is a typical block diagram of the electric power steering apparatus by which the magnetostrictive torque sensor which concerns on a prior art is mounted. It is front sectional drawing of the magnetostrictive torque sensor which concerns on a prior art. It is a torque detection circuit diagram applied to the magnetostrictive torque sensor according to the prior art. FIG. 24 is a characteristic diagram showing a relationship between an output voltage detected by a torque detection circuit of FIG. 23 and a steering torque signal.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the drawings referred to below, the same or corresponding parts as those shown in FIGS. 21 to 24 are designated by the same reference numerals, and detailed description thereof is omitted. Moreover, in order to avoid complication, it demonstrates with reference to the said FIGS. 21-24 as needed.

  FIG. 1 is a schematic configuration diagram of a pinion drive type electric power steering apparatus 10 in which a magnetostrictive torque sensor 144 (144A, 144B, 144C) according to first to fourth embodiments of the present invention is mounted (applied). is there.

  In FIG. 1, the electric power steering apparatus 10 includes a steering shaft 14 connected to a steering handle 12. The steering shaft 14 is configured such that a main steering shaft 16 integrally coupled to the steering handle 12 and a pinion shaft 22 provided with a pinion gear 20 of a rack and pinion mechanism 18 are connected by a universal joint 24. .

  The pinion shaft 22 is supported at the lower and intermediate portions thereof by bearings 26 a and 26 b provided in the gear housing 29 (29 a and 29 b), and the pinion gear 20 is provided at the lower end portion of the pinion shaft 22. The pinion gear 20 meshes with a rack gear 30 of a rack shaft 28 that can reciprocate in the vehicle width direction, and left and right front wheels 34 as steered wheels are connected to both ends of the rack shaft 28 via tie rods 32. As shown in FIG. 3, the back side of the rack gear 30 of the rack shaft 28 slides on the rack guide 47. A pressing force is applied to the rear surface side of the rack guide 47 through the other end of a rack guide spring 49 (compression spring) having one end seated on a rack guide screw 48 screwed into the rack housing 31.

  With this configuration, a normal rack and pinion type steering operation can be performed when the steering handle 12 is steered, and the direction of the vehicle can be changed by turning the front wheels 34. Here, the rack shaft 28, the rack gear 30 and the tie rod 32 constitute a steering mechanism 33.

  A steering system is constituted by the steering mechanism 33, the steering shaft 14 (the main steering shaft 16 connected by the universal joint 24, the pinion shaft 22 provided with the pinion gear 20 of the rack and pinion mechanism 18), and the steering handle 12. Composed.

  Further, the electric power steering apparatus 10 includes an electric motor (motor) 36 that supplies an auxiliary steering force for reducing the steering force by the steering handle 12 to the pinion shaft 22, and is provided on an output shaft 37 of the electric motor 36. The worm gear 38 (not shown in FIG. 1 but see FIG. 21) meshes with the worm wheel gear 40 provided on the upper side of the bearing 26b in the intermediate portion of the pinion shaft 22, as shown in FIG. Yes. The worm gear 38 and the worm wheel gear 40 constitute a speed reduction mechanism 42. The speed reduction mechanism 42 converts the rotation / driving force of the electric motor 36 into the rotation / driving force of the pinion shaft 22 smoothly and boosting.

  A magnetostrictive type for detecting the torque of the pinion shaft 22 (steering shaft 14) based on a change in magnetic characteristics due to magnetostriction, that is, a magnetic characteristic due to the inverse magnetostriction effect, is provided above the bearing 26b in the intermediate portion of the pinion shaft 22. A torque sensor 144 is arranged.

  FIG. 2 is also a schematic view of a column drive type electric power steering apparatus 10A on which the magnetostrictive torque sensor 144 (144A, 144B, 144C) according to the first to fourth embodiments of the present invention is mounted (applied). It is a block diagram.

  In this column drive type electric power steering apparatus 10A, a column shaft 11 (a rotating shaft made of steel, also referred to as a shaft member 23 as will be described later) is provided between the main steering shaft 16 and the universal joint 24. .

  The column shaft 11 is supported at its lower, middle and upper portions by bearings 27a, 27b and 27c.

  The electric power steering apparatus 10A includes an electric motor 36 that supplies an auxiliary steering force to the column shaft 11 to reduce the steering force by the steering handle 12, and a worm gear 38 provided on the output shaft of the electric motor 36 is provided. The worm wheel gear 40 is provided between the bearing 27b and the bearing 27a of the column shaft 11. The worm gear 38 and the worm wheel gear 40 constitute a speed reduction mechanism 42. The speed reduction mechanism 42 converts the rotation / driving force of the electric motor 36 into the rotation / driving force of the column shaft 11 smoothly and boosting.

  In this case, a magnetostriction for detecting the torque of the column shaft 11 (main steering shaft 16) based on a change in magnetic characteristics caused by magnetostriction is provided between the bearing 27b in the middle portion of the column shaft 11 and the upper bearing 27a. A type torque sensor 144 is arranged.

  Hereinafter, a first embodiment (magnetostrictive torque sensor 144) and a second embodiment (magnetostrictive torque sensor) of the magnetostrictive torque sensor mounted (applied) to the electric power steering apparatuses 10 and 10A shown in FIGS. 144A), the third embodiment (magnetostrictive torque sensor 144B), and the fourth embodiment (magnetostrictive torque sensor 144C) will be described by taking the pinion drive type electric power steering apparatus 10 shown in FIG. 1 as an example. To do.

[First embodiment]
A magnetostrictive torque sensor 144 according to a first embodiment of the present invention will be described.

  As shown in FIGS. 3 and 4, the magnetostrictive torque sensor 144 according to the first embodiment is a shaft member provided on a pinion shaft (shaft member) 22 of a rack and pinion mechanism 18 including a pinion gear 20 and a rack gear 30. (Rotating shaft made of steel) 23, provided on the entire outer periphery of the outer periphery 23, and provided with an anisotropy in the opposite direction (magnetic anisotropy), two upper and lower first anisotropies ma1 and ma2 (different DC magnetic field is generated in the magnetostrictive film mf having the first magnetostrictive portion (NiFe plating) mf1, the second magnetostrictive portion (NiFe plating) mf2, the first magnetostrictive portion mf1, and the second magnetostrictive portion mf2 to which the isotropic ma) is applied. The first and second magnetic flux generators (also referred to as field generators or magnetic flux generators. Here, permanent magnets) 101 and 102 and the magnetic flux (magnetic field) of the first and second magnetic flux generators 101 and 102 are magnetostricted. Output (apply) to the membrane mf, many Has first and second yokes 111 and 112 for the flow of bundles stably, the. As shown in FIG. 4, in the first embodiment, the first magnetostrictive portion mf1 and the second magnetostrictive portion mf2 are provided in one magnetostrictive film mf. However, two magnetostrictive films are provided, The first magnetostrictive portion mf1 may be provided in the magnetostrictive film, and the second magnetostrictive portion mf2 may be provided in the other magnetostrictive film.

  Each of the first and second yokes 111 and 112 has a substantially arc shape in which magnetic thin plates (soft iron) are laminated, that is, has a laminated structure of arc-shaped magnetic material thin plates, and the vortex is formed by the laminated structure. It has a configuration that can suppress the generation of current. The first and second yokes 111 and 112 have the same shape, and are formed in an arc shape that is larger than the diameter of the shaft member 23 and rides on a concentric circle having a larger diameter than the circumference of the shaft member 23. .

  A magnetic field generation section (first field magnet section) 211 is formed by the magnetic flux generation section 101 and the first yoke (also simply referred to as a yoke) 111, and the magnetic flux generation section 102 and the second yoke (also referred to simply as a yoke). ) 112 forms a field portion (second field portion) 212.

  The magnetostrictive torque sensor 144 detects a change in magnetic permeability of the magnetostrictive film mf (mf1, mf2) that changes according to the torsional torque applied to the shaft member 23.

  FIG. 5 is a schematic cross-sectional explanatory view on the first field magnet portion 211 side of the magnetostrictive torque sensor 144 according to the first embodiment shown in FIGS. 3 and 4.

  As shown in FIG. 5, the change in the magnetic permeability of the magnetostrictive film mf (mf1, mf2) formed on the shaft member 23 is not shown in the first yoke 111 and the second yoke 112 (not shown in FIG. 5). The magnetic flux φ flowing through the first yoke 111 is changed, and the change in the magnetic flux φ at this time is changed by the first magnetic flux detection unit (magnetic field detection unit) 121 sandwiched between the first yoke 111 and the second magnetic flux detection unit sandwiched between the second yokes 112. (Magnetic field detection unit) 122 detects. The first and second magnetic flux detection units 121 and 122 are also referred to as magnetic field detection elements {magnetic flux detection elements or magnetic flux (magnetic field) detection devices such as Hall elements. }. As the magnetic field detection element, a magnetoresistive element (MR element) or the like can be used in addition to the Hall element.

  The first and second magnetic flux generators 101 and 102 can use electromagnets instead of permanent magnets. In the case of using an electromagnet, for example, in FIG. 5, the yoke 111a is extended to the position occupied by the magnetic flux generator 101, which is a permanent magnet, and a winding (coil) is applied to the extended yoke 111a. A configuration in which current (DC current, steady current) is allowed to flow is good.

  FIG. 6 is an explanatory perspective view of the magnetostrictive torque sensor 144 including the first and second sensor housings 131 and 132.

  As described above, the magnetostrictive torque sensor 144 basically includes a magnetic field generation unit 101 (102) and a yoke 111 (112) engaged with the magnetic flux generation unit 101 (102). Part 211 (212), magnetostrictive part mf1 (mf2) having magnetic anisotropy ma1 (ma2) provided over the entire circumference of part of the surface of shaft member 23, and magnetic flux flowing through yoke 111 (112) and a magnetic flux detector 121 (122) for detecting a change based on the twist of the shaft member 23 of φ.

  In the following description, in order to avoid complications, the first sensor housing 131 including the upper first magnetostrictive portion mf1, the first yoke 111, and the like will be basically described as an example, and the lower second The second sensor housing 132 including the magnetostrictive portion mf2 and the second yoke 112 will be described as necessary.

  As shown in FIG. 5, the yoke 111 extends from the magnetic flux generator 101 in both directions along the circumferential direction of the shaft member 23, and the yoke 111 (111 a, 111 b) extends in both directions. The open ends 220 (220a, 220b) are arranged symmetrically with respect to the shaft center (axial center) of the shaft member 23, and the open ends 220 (220a, 220b) of the shaft member 23 are The teeth 222 (222a, 222b) have a convex shape toward the axis O (circumferential surface). In addition, the site | part which opposes the surrounding surface of the shaft material 23 of the teeth 222 is a concentric circle of the shaft material 23, and has a partially notched shape of the cylindrical inner surface. In this first embodiment, the angle θ formed by two lines connecting the teeth 222a and 222b and the axis (axis center) O is selected to be 180 °. That is, the teeth 222 a and 222 b are located on the opposite side with respect to the axis O. The angle θ formed by two lines connecting the teeth 222a and 222b and the axis O can be set to 90 ° ≦ θ ≦ 180 °.

  Then, the magnetic flux φ is output from the N pole of the magnetic flux generation unit 101 through one yoke 111a and one tooth 222a, and the magnetic flux φ passed through both circumferential directions (substantially the entire circumference) of the magnetostrictive portion mf1 is changed to the other tooth 222b. The magnetic path to the S pole of the magnetic flux generation unit 101 is formed by passing the magnetic flux φ through the other yoke 111b, and the magnetic flux detection unit 121 is provided in the magnetic path. It should be noted that the magnetic flux density B [mT] of the magnetic flux φ output from the magnetic flux generation unit 101 changes according to the change in the relative permeability μs of the magnetostrictive part mf1.

  In the first embodiment, the magnetic flux detection unit 121 is provided between the S pole of the magnetic flux generation unit 101 and the end of the yoke 111b, but the magnetic flux detection unit 121 is provided at any position in the yoke 111. Also good.

  In this case, the magnetic flux detection unit 121 is arranged with its magnetic sensitive surface parallel to the cross section of the yoke 111 (the cross section in which the magnetic flux φ is orthogonal). That is, the magnetic flux detector 121 is arranged so that the magnetic sensitive surface is orthogonal to the magnetic flux φ so that the detection sensitivity is high.

  As shown in FIG. 6, the first and second sensor housings 131 and 132 are configured by magnetic flux generation units 101 and 102, yokes 111 and 112, magnetic flux detection units 121 and 122, and resin molds 141 and 142, respectively. .

  FIG. 7 shows a circuit diagram of a detection circuit 153 including a first detection circuit 151 supported by the resin mold 141 and a second detection circuit 152 supported by the resin mold 142.

  As shown in FIGS. 6 and 7, in the first sensor housing 131, the yoke 111, the magnetic flux generation unit 101, and the magnetic flux detection unit 121 are integrally molded with resin in advance, and a power supply circuit is formed in a part of the resin mold 141. 162, and an assembly (assembly) in which the first detection circuit 151 configured by the amplification circuits 164 and 168 is mounted.

  In the second sensor housing 132, the yoke 112, the magnetic flux generation unit 102, and the magnetic flux detection unit 122 are integrally molded with a resin in advance, and a second detection circuit configured by a second amplification circuit 166 is partially formed on the resin mold 142. Assume that the assembly 152 is mounted thereon.

  That is, the magnetostrictive torque sensor 144 includes an assembly of the first sensor housing 131 and the second sensor housing 132 in which the first detection circuit 151 and the second detection circuit 152 are mounted in the vertical direction.

  1 and 2, 12 [V] is supplied from the ECU 110 to the power supply circuit (regulator) 162 built in the first detection circuit 151 (FIG. 7) via a lead wire and a coupler (connector) 170 (see FIG. 3). ] Of power Vbb is supplied.

  As shown in FIG. 7, a stabilized power supply Vcc of 5 [V] is generated by the power supply circuit 162, and the power supply Vcc includes first and second magnetic flux detectors 121 and 122 each including a Hall element, and a first amplification. The circuit 164, the differential amplifier circuit 168, and the second amplifier circuit 166 are supplied.

  The magnetic flux detectors 121 and 122 generate an output voltage corresponding to a magnetic flux (magnetic field) φ orthogonal to the magnetic sensing surface of the Hall element through which the control current is passed. The first and second amplifier circuits 164 and 166 amplify this voltage and output an output voltage VT1 and an output voltage VT2.

  Further, the differential amplifier circuit 168 generates a differential voltage between the output voltage VT1 and the output voltage VT2, and outputs a steering torque signal VT3. The output voltage VT1, the output voltage VT2, and the steering torque signal VT3 are transmitted through the coupler 170 to the ECU 110 (FIGS. 1 and 2) that is a control device.

  Based on the steering torque signal VT3, the vehicle speed signal Vs from the vehicle speed sensor 13, and the motor rotation signal from the rotation speed sensor of the electric motor 36, the ECU 110 calculates a target motor current for causing the electric motor 36 to generate power.

  The ECU 110 generates the target current by converting it into a drive voltage (PWM signal) for energizing the electric motor 36, and detects the actual motor current that is actually energized to the electric motor 36 with a current sensor. PI (proportional integral) control is performed so that the current and the actual motor current coincide with each other to generate power in the motor 36.

  As shown in FIG. 3, the power of this motor is transmitted to the steering shaft 14 (main steering shaft 16) via the speed reduction mechanism 42 (worm gear 38 and worm wheel gear 40) provided on the pinion shaft 22, and the driver. The steering load is reduced.

  Further, as described above, ECU 110 performs failure detection using output voltage VT1 and output voltage VT2. That is, it is monitored whether the sum of the output voltage VT1 and the output voltage VT2 (VT1 + VT2) is within a predetermined range (in the example of FIG. 24, a range of + 2.5V ± ΔV). Judged as a failure.

  As shown in FIG. 8A, after the magnetostrictive film mf is formed on the shaft member 23, heat treatment is performed in a state where a predetermined torsion torque (right torque) is applied to the shaft member 23, and after naturally cooling, the torsion torque is removed. . Thereby, the first anisotropy ma1 is provided in the upper magnetostrictive portion mf1.

  The heat treatment at this time is performed for a predetermined time by high-frequency heating. The magnetostrictive film mf is preferably made of NiFe (iron nickel) as a main component and has a predetermined torsional torque of 50 [Nm] or more and 100 [Nm] or less.

  After providing the first anisotropy ma1, as shown in FIG. 8B, heat treatment is performed in a state where a predetermined torsion torque (left torque) is applied in the opposite direction, and after naturally cooling, the torsion torque is removed. Thereby, the second anisotropy ma2 is provided in the lower magnetostrictive portion mf2.

  FIG. 9 shows a characteristic 181 showing the relationship between the input torque Ts [Nm] of the shaft member 23 after the anisotropy ma (ma1, ma2) is applied and the relative permeability μs of the magnetostrictive film mf (mf1, mf2), 182. By providing the anisotropy ma1 and ma2, for example, the relative magnetic permeability μs increases in the first magnetostrictive portion mf1 with respect to the input torque Ts [Nm] (0 to 50 right torque), and the second magnetostrictive portion. At mf2, the relative permeability μs decreases. The relative magnetic permeability μs decreases in the first magnetostrictive portion mf1 and the relative magnetic permeability μs increases in the second magnetostrictive portion mf2 with respect to the input torque Ts [Nm] (left torque of 0 to −50) in the reverse direction.

  10 shows the input torque (steering torque) Ts [when the magnetic force of the magnetic flux generators 101 and 102 is applied to the magnetostrictive portions mf1 and mf2 having the characteristics 181 and 182 shown in FIG. Among the characteristics indicating the change in the magnetic flux density B [mT] of the yokes 111 and 112 with respect to Nm], characteristics 191 and 192 in the actual use range (± 15 [Nm]) as the magnetostrictive torque sensor 144 are shown.

  For example, in the first magnetostrictive portion mf1, the magnetic flux density [mT] increases as the input torque Ts [Nm] of the right torque increases.

  11A, FIG. 11B, and FIG. 11C are schematic diagrams showing changes in the magnetic flux density of the yoke 111 at this time.

  Since the magnetic permeability at point a on the characteristic 191 in FIG. 10 is small, as shown in FIG. 11A, the magnetic flux density B [mT] of the yoke 111 is small (195 [mT]), and the magnetic permeability is large at point c. As shown in FIG. 11C, the magnetic flux density B [mT] of the yoke 111 is large (205 [mT]). At a point b where the input torque Ts [Nm] is 0, as shown in FIG. 11B, the magnetic flux density B [mT] is intermediate (200 [mT]).

  That is, the magnetic flux density B [mT] of the magnetic flux φ flowing in the field portion 211 changes based on the change in the relative permeability μs of the magnetostrictive portion mf1 that changes according to the input torque Ts [Nm] applied to the shaft member 23. Will do. Referring to FIGS. 11A to 11B, the magnetic flux φ itself generated from the N pole of the magnetic flux generation unit 101 of the field unit 211 is increased or decreased by the magnetostriction unit mf1 in which the relative permeability μs increases or decreases. The magnetic flux detecting unit 121 is provided in the magnetic path through which the increased or decreased magnetic flux φ returns to the S pole of the magnetic flux generating unit 101 of the field magnet unit 211.

  The field part 211 composed of the magnetic flux generation part 101 and the yoke 111 is an assembly (assembly) integrally constituted by the magnetic flux detection part 121 and the resin mold 141 (FIG. 6).

  According to the magnetostrictive torque sensor 144 of the first embodiment described above, the magnetic flux φ due to the static magnetic field generated by the magnetic flux generators 101 and 102 is output via the yokes 111 and 112, and the output magnetic flux φ is the shaft material. Since the magnetic flux φ passing through the magnetostrictive portions mf1 and mf2 of the magnetostrictive film mf2 provided in the magnetostrictive film mf2 and passing through the magnetostrictive portions mf1 and mf2 is detected by the magnetic flux detecting portions 121 and 122 via the yokes 111 and 112, Thus, since it is not necessary to use the four detection coils 51 to 54 that are used for multiple excitation as described above, it is possible to reduce the size and weight and pass the magnetic flux φ through the yokes 111 and 112. Can be detected by the magnetic flux detectors 121 and 122 through the magnetostrictive portions mf1 and mf2 with high efficiency (high magnetic flux density). As a result, detection accuracy (detection sensitivity) can be increased, and robustness (toughness) against external electromagnetic noise can be improved.

  Further operational effects of the magnetostrictive torque sensor 144 according to the first embodiment will be described in the section “Summary of Embodiments” to be described later.

[Second Embodiment]
Next, a magnetostrictive torque sensor 144A according to a second embodiment of the present invention will be described with reference to FIGS.

  The magnetostrictive torque sensor 144A according to the second embodiment includes yokes 111P and 111Q having different shapes compared to the magnetostrictive torque sensor 144 according to the first embodiment.

  The upper yoke 111P will be described as an example. The yoke 111 </ b> P is a first and second yoke 111 a, 111 b in both directions along the circumferential direction of the shaft member 23 from the magnetic flux generation unit 101, and is opposed to the axis O of the shaft member 23 (180 at the central angle). Extending in a circular arc shape to a position of 0 °, further extending slightly toward the axis O, and further extending from the first and second yokes 111a and 111b in both the outer and inner directions along the circumferential direction of the shaft member 23, respectively. The first branch yoke 301 is formed in a direction away from the first yoke 111a (outward direction) and the second branch yoke 302 is formed in a direction approaching the first yoke 111a (inward direction). On the other hand, the third branch yoke 303 is formed in the direction away from the second yoke 111b (outside direction), and the fourth branch yoke 3 in the direction closer to the second yoke 111b (inward direction). 4 and the first branch yoke 301 and the fourth branch yoke 304 have open ends arranged symmetrically (opposite to each other) with respect to the axis O of the shaft member 23, and each open end is The first teeth 401 and the fourth teeth 404 are convex toward the axis O (circumferential surface) of the shaft member 23, and the second branch yoke 302 and the third branch yoke 303 are the axis centers of the shaft member 23. Second teeth 402 having open ends arranged symmetrically (opposite to each other) with respect to O, each open end having a convex shape toward the axis O (circumferential surface) of the shaft member 23; The third tooth 403 is used.

  Under such a configuration of the yoke 111P, the magnetic flux φ from the N pole of the magnetic flux generation unit 101 through the first yoke 111a, the first branch yoke 301, and the first teeth 401 is transferred to the upper peripheral surface (surface) in FIG. The magnetic flux φ that is output and passed through the circumferential direction on one side of the magnetostrictive portion mf1 is input to the third tooth 403, and the magnetic flux φ is passed through the third branch yoke 303 and the second yoke 111b. While forming the first magnetic path to the S pole, the magnetic flux φ is output from the magnetic flux generator 101 through the first yoke 111a, the second branch yoke 302, and the second tooth 402, and is opposed to the axis O of the magnetostrictive portion mf1. The magnetic flux φ passed through the circumferential direction on the other side is input to the fourth tooth 404 and passed through the fourth branch yoke 304 and the second yoke 111b to reach the S pole of the magnetic flux generation unit 101. First Forming a magnetic path, and a structure in which a magnetic flux detecting unit 121 in the combined said first path and said second path.

  In the magnetostrictive torque sensor 144A according to the second embodiment configured as described above, a plurality (four) of teeth 401 to 404 for passing the magnetic flux φ through the magnetostrictive portions mf1 and mf2 are provided. As a result, even if the yokes 111P and 111Q and the shaft center O (center of rotation) of the shaft member 23 are deviated, the magnetic flux φ is averaged, so that changes in the output voltages VT1, VT2 and the steering torque signal VT3 are suppressed. can do. More specifically, when one of the gaps (gap) of the magnetostrictive portions mf1 and mf2 and the teeth 401 to 404 is narrowed, the other is widened so that the magnetic flux densities of the yokes 111P and 111Q are averaged and do not change. In the second embodiment, two teeth 401 to 404 are provided on one side. However, three teeth 405 and 406 are further provided on one side at the position indicated by a two-dot chain line shown in FIG. Or more than that may be provided.

  In the second embodiment, the first magnetostrictive portion mf1 and the second magnetostrictive portion mf2 are provided in one magnetostrictive film mf. However, two magnetostrictive films are provided, and one magnetostrictive film is provided on one magnetostrictive film. The first magnetostrictive portion mf1 may be configured such that the second magnetostrictive portion mf2 is provided on the other magnetostrictive film.

[Third embodiment]
Next, a magnetostrictive torque sensor 144B according to a third embodiment of the present invention will be described with reference to FIG.

  This magnetostrictive torque sensor 144B is non-magnetic between the magnetostrictive film mf (mf1, mf2) and the shaft member (steel material) 23 as compared with the magnetostrictive torque sensor 144 (see FIG. 6) according to the first embodiment. A body ring (a thin cylindrical body, hereinafter referred to as a non-magnetic ring) 410 is provided.

  The nonmagnetic ring 410 is formed, for example, by plating the shaft member 23 with copper, and NiFe plating is performed on the nonmagnetic ring 410 to form the magnetostrictive portions mf1 and mf2. Alternatively, a copper cylindrical tube (circular tube) may be press-fitted into the shaft member 23, and NiFe plating may be performed on the nonmagnetic ring 410 to form the magnetostrictive portions mf1 and mf2. The nonmagnetic ring 410 is not limited to copper but may be made of aluminum or nonmagnetic stainless steel.

  By providing the non-magnetic ring 410, the magnetic flux φ passing through the magnetostrictive portions mf1 and mf2 becomes difficult to enter the shaft member 23. In other words, the leakage flux to the shaft member 23 is reduced, and the detection sensitivity is correspondingly reduced. The signal-to-noise ratio (signal-to-noise ratio) increases.

  In addition, a magnetic flux (not shown) flowing from the outside to the shaft member 23, for example, a magnetic flux caused by engine noise, a magnetic flux caused by another motor current, a magnetic flux caused by a horn current, and the like is blocked by the nonmagnetic ring 410. Therefore, the noise magnetic flux flowing through the magnetostrictive portions mf1 and mf2 is reduced, and the robustness (toughness) against external noise is further improved.

  In the third embodiment, the first magnetostrictive portion mf1 and the second magnetostrictive portion mf2 are provided in one magnetostrictive film mf. However, two magnetostrictive films are provided, and one magnetostrictive film is provided on one magnetostrictive film. The first magnetostrictive portion mf1 may be configured such that the second magnetostrictive portion mf2 is provided on the other magnetostrictive film.

[Fourth embodiment]
Next, a magnetostrictive torque sensor 144C according to a fourth embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 15, in the magnetostrictive torque sensor 144C, two field portions 211a and 211b are provided for the magnetostrictive portion mf1 having the first anisotropy ma1 located above the shaft member 23.

  The field magnet portion 211a includes a magnetic flux generator 101a and an arcuate yoke 111x extending from the magnetic flux generator 101a on both sides. The field magnet portion 211b includes a magnetic flux generator 101b and an arcuate yoke 111y extending from the magnetic flux generator 101b to both sides. The field magnet portions 211 a and 211 b are arranged point-symmetrically with respect to the axis O of the shaft member 23. A magnetic flux detector 121a is provided for the field magnet 211a, and a magnetic flux detector 121b is provided for the field magnet 211b.

  The arc-shaped length from the teeth 220c to the teeth 220d of the yoke 111x and the arc-shaped length from the teeth 220e to the teeth 220f of the yoke 111y are the central angle θ1 formed by the axis O, the teeth 220c and the teeth 220d, and A central angle θ1 formed by the axis O, the teeth 220e, and the teeth 220f is set in a range of θ1 <180 °.

  Although not shown, two field portions 211a ′ and 211b ′ are similarly provided for the magnetostrictive portion mf2 having the second anisotropy ma2 located below the shaft member 23. Magnetic flux detectors 121a 'and 121b' are provided for the two field portions 211a 'and 211b', respectively.

  In this case, as shown in the circuit diagram of the torque detection circuit 153A according to the fourth embodiment of FIG. 16, the addition circuit 165 adds the outputs of the magnetic flux detection unit 121a and the magnetic flux detection unit 121b located on the magnetostriction unit mf1, The addition result is amplified by the first amplifier circuit 164 to obtain the output voltage VT1. That is, the magnetic change of the first anisotropy ma1 of the magnetostrictive portion mf1 is detected by the sum of the outputs of the two magnetic flux detectors 121a and 121b.

  Further, the outputs of the magnetic flux detection unit 121a ′ and the magnetic flux detection unit 121b ′ located on the magnetostriction unit mf2 are added by the addition circuit 167, and the addition result is amplified by the second amplification circuit 166 to obtain the output voltage VT2. That is, the magnetic change of the second anisotropy ma2 of the magnetostrictive portion mf2 is detected by the sum of the outputs of the two magnetic flux detectors 121a ′ and 121b ′.

  These output voltage VT1 and output voltage VT2 are differentially amplified by a differential amplifier circuit 168 to obtain a steering torque signal VT3.

  As a result, even if the yokes 111x and 111y and the shaft center (center of the rotation axis) O of the shaft member 23 are displaced, the magnetic flux φ is averaged, that is, the magnetic flux detection unit that moves away, for example, Although the detected magnetic flux φ at the magnetic flux detectors 121a and 121a ′ decreases, the detected magnetic flux φ at the closer magnetic flux detector, in this case, the magnetic flux detectors 121b and 121b ′ increases, so the sum is the same result. Thus, changes in output can be suppressed. Moreover, the detection sensitivity is doubled.

  In the fourth embodiment, the first magnetostrictive portion mf1 and the second magnetostrictive portion mf2 are provided in one magnetostrictive film mf. However, two magnetostrictive films are provided, and one magnetostrictive film is provided on one magnetostrictive film. The first magnetostrictive portion mf1 may be configured such that the second magnetostrictive portion mf2 is provided on the other magnetostrictive film.

[Summary of Embodiment]
As described above, according to the above-described embodiment, for example, the magnetostrictive torque sensor 144 according to the first example described with reference to FIGS. 1 to 11C is provided on the shaft member 23 and the shaft member 23. Magnetostrictive films mf (mf1, mf2) as magnetostrictive materials having magnetic anisotropies ma1, ma2 and field portions 211, 212 (FIG. 4) for outputting magnetic flux φ passed through the magnetostrictive films mf (mf1, mf2) And magnetic flux detectors 121 and 122 for detecting the magnetic flux φ output from the field magnets 211 and 212 and passing through the magnetostrictive film mf (mf1, mf2), and the shaft material based on the detection results of the magnetic flux detectors 121 and 122 23, a torque detection circuit 153 (FIG. 7) serving as a torque detection unit that detects the steering torque Ts applied to the control unit 23 is provided.

  In this case, the field magnet portions 211 and 212 include small-volume magnetic flux generating portions 101 and 102 that generate a magnetic flux φ due to a static magnetic field, and yokes 111 and 112 engaged with the magnetic flux generating portions 101 and 102, The magnetic flux φ generated by the magnetic flux generators 101 and 102 is guided to the yokes 111 and 112 functioning as magnetic flux paths having a small magnetic resistance, and output (passed) through the yokes 111 and 112, and the output magnetic flux φ is output. Is passed through a magnetostrictive film mf (mf1, mf2) provided on the shaft member 23.

  In this way, the magnetic flux φ due to the static magnetic field generated by the magnetic flux generators 101 and 102 is output through the yokes 111 and 112, and the magnetostrictive film mf (mf1, mf2) provided with the output magnetic flux φ on the shaft member 23 is output. ), The magnetic flux φ passing through the magnetostrictive film mf (mf1, mf2) is detected by the magnetic flux detectors 121 and 122, so that the size can be reduced and the magnetic flux φ is passed through the yokes 111 and 112. The magnetic flux φ generated by the units 211 and 212 can be detected by the magnetic flux detection units 121 and 122 through the magnetostrictive films mf (mf1 and mf2) with high efficiency (high magnetic flux density). As a result, the detection accuracy (detection sensitivity) can be increased, and the robustness (toughness) against external electromagnetic noise is improved.

  As the magnetic flux generators 101 and 102 that generate a static magnetic field that does not vary with time, a permanent magnet or an electromagnet can be used. As the electromagnet, a coil may be wound around the yokes 111 and 122 to form a solenoid, and a constant direct current may be passed through the solenoid.

  Using a permanent magnet eliminates the need for a power source for the magnetic flux generator. As the magnetic flux detection units 121 and 122, a magnetic sensor (magnetic flux detection device) such as a Hall element or a magnetoresistive element can be used.

  In this case, the yokes 111 and 112 are formed in an arc shape extending in both directions along the circumferential direction of the shaft member 23 from the magnetic flux generators 101 and 102, and both open ends of the yokes 111 and 112 forming the arc shape are These are teeth 222 (222a, 222b) each having a convex shape extending toward the axis O of the shaft member 23. For example, as shown in FIG. The magnetic flux φ is output through the teeth 222a, and the magnetic flux φ divided on both sides of the magnetostrictive portion mf1 and passing through the surface is input to the other teeth 222b, and the magnetic flux φ is passed through the yoke 111b and returned to the S pole of the magnetic flux generating portion 101. To form a magnetic path. The magnetic flux detector 121 is provided in the magnetic path.

  Since the arc-shaped yoke 111 is formed in a semicircular shape (center angle 180 °), the magnetic flux φ passing in the circumferential direction of the magnetostrictive portion mf1 is arranged symmetrically (respectively on the opposite side) with respect to the axis O. Since the magnetic flux φ circulates on both sides in the circumferential direction of the magnetostrictive portion mf1, the magnetic flux in the portions of the teeth 222a and 222b is generated even when the yoke 111 is displaced with respect to the shaft. The density does not change and the magnetic flux φ can be detected stably. In other words, since the magnetic flux φ passes through the entire circumference of the magnetostrictive portion mf1, the characteristics are averaged even if the film thickness of the magnetostrictive portion mf1 is not uniform, and as a result, accurate torque can be detected.

  The effects of forming the arc-shaped yoke 111 on a semicircular circumference (center angle 180 °) will be further described with reference to FIGS. 17A, 17B, 18A, and 18B.

  As shown in FIG. 17A, when the shaft member 23 and the center 310 of the yoke 111 (the line connecting the ends of the arc) coincide with each other, the magnetic path m1 and the magnetic path on the magnetostrictive portion mf1 of the shaft member 23 Since the lengths of n1 are equal (m1 = n1) and the magnetic resistance is the same, the magnetic flux φ flows evenly through the magnetostrictive portion mf1.

  For example, as shown in FIG. 17B, even when the shaft member 23 and the center 310 of the yoke 111 are displaced, the length of one magnetic path m2 is increased (m2> m1 = n1), and the magnetic resistance is increased. Even if the magnetic flux φ is increased and the length of the other magnetic path n2 is shortened (n2 <m2), the magnetic resistance is decreased and the magnetic flux φ is increased, so that the entire magnetostrictive portion mf1 and the yoke 111 flow. The amount of magnetic flux φ does not change. Thus, according to the magnetostrictive torque sensor 144, accurate torque detection is possible even when the shaft member 23 and the center 310 of the yoke 111 are displaced.

  In addition, since the magnetostrictive torque sensor 144 has the arc-shaped yoke 111 corresponding to the semicircular circumference, the film thickness of the magnetostrictive portion mf1 is not uniform or the composition is not uniform. Even if the magnetic resistance differs with respect to the rotational phase, the torque can be detected accurately. For example, in FIG. 18A, the magnetostriction portion mf1x has a thick film thickness on the half circumference of the shaft member 23 near the yoke 111 side, and in FIG. 18B, the magnetostriction has a thick film thickness on the half circumference of the shaft material 23 far from the yoke 111. The part is mf1y.

  Even in the magnetostrictive portions mf1x and mf1y whose thicknesses are biased as shown in FIGS. 18A and 18B, the magnetic flux φ passes through the entire circumference of the magnetostrictive portion mf1, and thus the characteristics of the magnetostrictive portion mf1 are averaged. Therefore, the magnetic flux φ passing through the magnetostrictive portion mf1 and the yoke 111 is constant regardless of the rotational phase, so that the magnetic flux φ can be accurately detected by the magnetic flux detecting portion 121, and thus accurate torque can be detected.

  Further, in the magnetostrictive torque sensors 144, 144A, 144B, and 144C according to the first to fourth embodiments, the multi-winding detection coils 51 to 54 for multiple excitation shown in FIGS. 21 to 23 are not used. The steering torque Ts can be detected, and the size and weight can be reduced.

[Application of bias magnetic field]
In the magnetostrictive torque sensors 144, 144A, 144B, and 144C according to the first to fourth embodiments described above, the magnetostrictive torque sensors 144, 144A, and 144B are applied in a region where the magnetic permeability μ is stable by applying the bias magnetic field Hbias to the magnetostrictive film mf. 144C is used.

  In this case, as shown in the BH curve of FIG. 19, a bias magnetic field Hbias sufficient to saturate the magnetic flux density B of the magnetostrictive film mf that is equal to or greater than the holding force Hc of the magnetostrictive film mf may be applied to the magnetostrictive film mf. . In FIG. 19, the residual magnetic flux density Br and the saturation magnetic flux density Bs are also entered.

  When the bias magnetic field Hbias is applied to the magnetostrictive film mf, the shaft member 23 is magnetized, a permanent magnet is disposed on the shaft member 23, or a coil is wound around the shaft member 23 and a DC power source is connected to the coil. For example, various configurations can be adopted.

  By applying a bias magnetic field Hbias to the magnetostrictive film mf, the output voltages V1, V2 and the steering torque signal VT3 are stabilized.

  In the magnetostrictive torque sensors 144, 144A, 144B, and 144C according to the first to fourth embodiments described above, the bias magnetic field Hbias is applied by the permanent magnets as the magnetic flux generators 101 and 102 that constitute the field magnets 211 and 212 and the like. ing.

  When the magnetic field strength H changes in a region where the BH curve has a large slope due to an external magnetic field and rises from the origin in FIG. 19, the magnetic flux density B becomes unstable, resulting in the first and second magnetic fluxes. The output voltages VT1 and VT2 as detection values detected by the detection units 121 and 122 are not stable. In order to prevent this, an area where the slope of the BH curve is less than the holding force Hc is used. For this reason, a bias magnetic field Hbias having a holding force Hc or more is applied in advance to the magnetostrictive film mf.

  FIG. 20 shows a change in the magnetic permeability μ with respect to the magnetic field strength H by the slope (differential value) of the initial magnetic permeability curve when the magnetic field strength H increases from zero in the BH curve of FIG. Is what we asked for. By applying a bias magnetic field equal to or greater than the bias magnetic field Hbias shown in FIG. 20 to the magnetostrictive film mf, even if the magnetic field strength H changes due to the influence of an external magnetic field or the like, the magnetic permeability μ [H / m] changes greatly. The magnetostrictive torque sensors 144, 144A, 144B, and 144C can be used in a stable region having a magnetic permeability μ [H / m].

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification.

DESCRIPTION OF SYMBOLS 10, 10A ... Electric power steering apparatus 12 ... Steering handle 14 ... Steering shaft 16 ... Main steering shaft 22 ... Pinion shaft 23 ... Shaft material 36 ... Electric motor (motor)
44, 144, 144A to 144C ... Magnetostrictive torque sensors 101, 101a, 101b, 102 ... Magnetic flux generator 110 ... ECU
111, 111a, 111b, 111P, 111Q, 111x, 111y, 112 ... yoke 121, 122 ... magnetic flux detector 131 ... first sensor housing 132 ... second sensor housing 141, 142 ... resin mold 151, 152, 153 ... detection circuit 211, 211a, 211b, 212 ... field portions 220, 220a, 220b ... open ends 222, 222a-222f, 401-406 ... teeth 301-304 ... branch yoke 310 ... center 410 ... non-magnetic ring

Claims (5)

Shaft material,
A magnetostrictive material having magnetic anisotropy provided on the shaft material;
A field portion for outputting a magnetic flux passed through the magnetostrictive material;
A magnetic flux detection unit that detects the magnetic flux output from the field part and passed through the magnetostrictive material;
A torque detection unit that detects torque applied to the shaft member based on a detection result of the magnetic flux detection unit;
A magnetostrictive torque sensor comprising:
The field portion includes e Bei magnetic flux generator for generating a magnetic flux by the static magnetic field, a yoke engaged with the magnetic flux generating portion,
The yoke is formed to extend in both directions along the circumferential direction of the shaft member from the magnetic flux generating portion, and both open ends of the yoke have convex shapes extending from the yoke toward the shaft center of the shaft member, respectively. Teeth to be presented,
The outputs the magnetic flux through the yoke and one of the teeth from the magnetic flux generating unit, the outputted magnetic flux is passed in the circumferential direction of the magnetostrictive material provided on the shaft member, the magnetic flux through the magnetostrictive material The magnetic path is formed by inputting the magnetic flux to the other tooth and returning the magnetic flux to the yoke and returning the magnetic flux to the magnetic flux generation section, and the magnetic flux detection section is provided in the magnetic path,
The yoke is formed in an arc shape,
The central angle of the arc of the yoke formed in the arc shape is less than 180 °,
A magnetostrictive torque sensor characterized in that an assembly composed of the field magnet part and the magnetic flux detection part is provided point-symmetrically with respect to the axis of the shaft member . The magnetostrictive torque sensor according to claim 1,
The polarities of the magnetic flux generating parts constituting the field parts in the assemblies provided point-symmetrically with respect to the shaft center of the shaft material are the magnetic fluxes passing through the circumferential directions of the magnetostrictive material. The direction is set so that they are opposite or in the same direction with respect to the axis.
A magnetostrictive torque sensor. Shaft material,
A magnetostrictive material having magnetic anisotropy provided on the shaft material;
A field portion for outputting a magnetic flux passed through the magnetostrictive material;
A magnetic flux detection unit that detects the magnetic flux output from the field part and passed through the magnetostrictive material;
A torque detection unit that detects torque applied to the shaft member based on a detection result of the magnetic flux detection unit;
A magnetostrictive torque sensor comprising:
The field portion includes a magnetic flux generating portion that generates a magnetic flux by a static magnetic field, and a yoke engaged with the magnetic flux generating portion ,
Before SL yoke may extend in both directions from said magnetic flux generating portion along the circumferential direction of the shaft member, where it extends thereof to form a plurality of branches yoke near the outer periphery of the shaft member, each said branch yokes The end portion is an open end, and the open end is formed with a plurality of teeth each having a convex shape toward the axial center of the shaft member,
The magnetic flux is output from the magnetic flux generating section through one of the yokes and the teeth formed in one of the branch yokes, and the magnetic flux passing through the magnetostrictive material is formed in the other branch yoke. A magnetic path is formed by causing the teeth to be input, passing the magnetic flux through the other branch yoke to the other yoke, and returning the magnetic flux to the magnetic flux generation section, and providing the magnetic flux detection section in the magnetic path .
Magnetostrictive torque sensor, wherein the this. Shaft material,
A magnetostrictive material having magnetic anisotropy provided on the shaft material;
A field portion for outputting a magnetic flux passed through the magnetostrictive material;
A magnetic flux detection unit that detects the magnetic flux output from the field part and passed through the magnetostrictive material;
A torque detection unit that detects torque applied to the shaft member based on a detection result of the magnetic flux detection unit;
A magnetostrictive torque sensor comprising:
The field portion includes a magnetic flux generating portion that generates a magnetic flux by a static magnetic field, and a yoke engaged with the magnetic flux generating portion ,
Before SL yoke extends from said magnetic flux generating portion to symmetrical positions with respect to the axis of the shaft member in both directions along the circumferential direction of the shaft member extends further towards the axis, each of said yoke, From the extended portion, it further branches and extends in both directions along the circumferential direction of the shaft member to form a total of four branch yokes in the form of arcs in the vicinity of the outer periphery of the shaft member. The portion is an open end, and the four open ends each have a convex shape toward the axis of the shaft, and a total of four teeth are formed.
The magnetic flux is output from the magnetic flux generator through the two teeth formed on one of the yokes, one of the two branch yokes, and one of the two branch yokes, and passes the magnetostrictive material. The magnetic flux is input to the two teeth formed in the other two branch yokes, and the magnetic flux is returned to the magnetic flux generation unit through the other two branch yokes and through the other yoke. A magnetic path is formed, and the magnetic flux detector is provided in the magnetic path .
Magnetostrictive torque sensor, wherein the this. The magnetostrictive torque sensor according to claim 4 , wherein
The magnetostrictive torque, wherein the four teeth are arranged in each of four regions formed by two lines orthogonal to each other through the shaft center in a cross section orthogonal to the shaft center. Sensor.

Images