JP2007248402A - Magnetostrictive type torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetostrictive type torque sensor 1 capable of making constant a distance between a magnetic characteristic changing part (magnetostrictive film) and a yoke to stabilize an output. <P>SOLUTION: This magnetostrictive type torque sensor 1 is provided with a freely rotatable shaft 4, the magnetic characteristic changing part 5 provided in the shaft 4 to change a magnetic characteristic by a torque applied to the shaft 4, and a detecting part 7 arranged opposedly to the magnetic characteristic changing part 5 with a prescribed distance, and for detecting a change of the magnetic characteristic of the magnetic characteristic changing part 5. The detecting part 7 is provided with coils 71, 72, and the yokes 73, 74 for holding the coils 71, 72. The yokes 73, 74 are energized axially by an energizing means 6, and are arranged with yoke tapered faces 73b, 74a formed in end parts of the yokes 73, 74, and fixing part tapered faces 8a, 8b formed in a fixing part 8 for holding the yokes 73, 74 onto a housing 2, while abutting each other therebetween. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a magnetostrictive torque sensor that is mounted on an electric power steering device such as an automobile and used for a detection device for magnetically detecting a steering torque applied to a shaft via a steering shaft.

  In general, an electric power steering apparatus installed in an automobile or the like detects torque applied from a steering shaft to a shaft by a torque sensor by a driver's steering operation. The electric power steering device drives and controls a motor for assisting the driver's steering operation (applying an auxiliary steering force) in accordance with a detection signal from the magnetostrictive torque sensor, and driving the driver's steering force. It is designed to give a comfortable steering feeling.

As a torque sensor in such an electric power steering device, a magnetostrictive torque sensor is known (for example, see Patent Document 1).
In this magnetostrictive torque sensor, a magnetostrictive film (for example, an Ni—Fe alloy film) having magnetic anisotropy is deposited on the surface of a shaft. When a torque is applied to the shaft from the outside, a change in the magnetic characteristics (permeability) of the magnetostrictive film according to the twist generated in the shaft is detected magnetically in contact.

Therefore, a conventional magnetostrictive torque sensor will be described by taking a magnetostrictive torque sensor used in an electric power steering apparatus of an automobile as an example.
FIG. 6 is a schematic diagram showing a conventional electric power steering apparatus.

  As shown in FIG. 6, the electric power steering apparatus 101 includes a magnetostrictive torque sensor 103 that detects a steering torque from the handle 102, a motor 104 that applies an auxiliary steering force to the operation of the handle 102, and the motor 104. A reduction device 105 that increases the rotational torque of the motor, an ECU (Electrical Control Unit) 107 that drives and controls the motor 104 in accordance with detection signals from the magnetostrictive torque sensor 103, the vehicle speed sensor 106, and the like, and the rotation of the motor 104 by the tire 108 , 108 to change the orientation of the tire 108, and a pinion gear 110. The reduction gear 105 is constituted by a worm 105A and a worm wheel 105B.

  In such an electric power steering apparatus 101, the steering torque when the driver operates the steering wheel is detected using the magnetostrictive torque sensor 103, and a detection signal (torque signal) from the magnetostrictive torque sensor 103 is detected by the ECU 107, The motor 104 is driven and controlled according to a detection signal (vehicle speed signal) from the vehicle speed sensor 106, and the torque of the motor 104 at this time is increased by the speed reducer 105 and the tire 108 is connected via the pinion gear 110 and the rack shaft 109. , 108.

  In this electric power steering apparatus 101, TH = TP / (1 + KA), where TH is the steering torque for steering operation, TP is the torque transmitted to the pinion gear 110, and KA is a constant related to the magnitude of the auxiliary torque by the motor 104. Thus, the driver's steering force can be reduced by the auxiliary torque of the motor 104.

Next, the magnetostrictive torque sensor 103 will be described with reference to FIG.
FIG. 7 is a cross-sectional view of an essential part showing an installation state of a magnetostrictive torque sensor in a conventional electric power steering apparatus.

  As shown in FIG. 7, the magnetostrictive torque sensor 103 is housed in a sensor housing case 111 including an upper case portion 111A and a lower case portion 111B. The magnetostrictive torque sensor 103 is connected to the steering shaft 102A (see FIG. 6) of the handle 102 (see FIG. 6), and is supported by the sensor housing case 111 so as to be rotatable via a bearing 112 and the like. Coils 115 and 116 which are detection means provided on the inner peripheral side of the upper case portion 111A so as to be vertically separated from each other, and are provided on the outer peripheral surface (outer surface) of the shaft 114 so as to face the coils 115 and 116, and are opposite to each other. The magnetostrictive films 117 and 118 having directional anisotropy are mainly configured.

  When the steering torque from the handle 102 (see FIG. 6) acts on the shaft 114, the change in the magnetic characteristics of the magnetostrictive films 117 and 118 corresponding to the torsion occurring in the shaft 114 is electrically generated on the coils 115 and 116 side, respectively. The direction and the magnitude of the steering torque applied to the shaft 114 are detected from this data.

Here, the upper case part 111A is formed of a light alloy such as an aluminum alloy or a magnesium alloy. The yokes 119 and 120 of the coils 115 and 116 are made of a soft magnetic electromagnetic steel sheet having high magnetic characteristics. The shaft (steering shaft) 114 is made of an iron alloy such as SC material or SCM material, and Fe—Ni-based or Fe—Cr-based magnetostrictive films 117 and 118 are provided on the outer peripheral surface thereof by plating or vapor deposition.
Japanese Unexamined Patent Publication No. 2004-239652 (paragraphs 0024 to 0034, FIG. 1 and FIGS. 7 to 9)

However, in the magnetostrictive torque sensor 103 as in Patent Document 1, the upper case portion 111A, the yokes 119 and 120, and the shaft 114 of the sensor housing case 111 shown in FIG. 7 are formed of different metal materials. Therefore, their linear expansion coefficients are different.
Comparing the iron alloy forming the yokes 119 and 120 and the shaft 114, the electromagnetic steel sheet forming the magnetostrictive films 117 and 118, the aluminum alloy forming the sensor housing case 111, etc., the linear expansion of the aluminum alloy The rate is nearly twice as large.
The environment in which the electric power steering apparatus 101 of the automobile is used is -40 ° C to 80 ° C, and there are cases where the temperature is more severe.

Therefore, when the temperature is low, the upper case portion 111A contracts relative to the yokes 119 and 120, so that the sensor housing case 111 pressurizes the yokes 119 and 120 from the axial direction and the radial direction. There is a point.
In the magnetostrictive torque sensor 103, the magnetic characteristics of the yokes 119 and 120 change due to this pressurization, and the yokes 119 and 120 formed by alternating energization of the coils 115 and 116, and the magnetostrictive films 117 and 118, There is a problem that the magnetic flux changes and the output changes.

On the other hand, when the temperature is high, the sensor housing case 111 expands relatively with respect to the yokes 119 and 120, thereby forming a gap a between the sensor housing case 111 and the yokes 119 and 120. There is a point.
In the magnetostrictive torque sensor 103, the gap a eliminates the amount of pressure applied between the yokes 119, 120 and the sensor housing case 111, and also causes rattling between the yokes 119, 120 and the sensor housing case 111. As a result, the magnetic flux between the yokes 119, 120 and the magnetostrictive films 117, 118 changes, and the output changes.

  Therefore, an object of the present invention is to provide a magnetostrictive torque sensor that can stabilize the output by keeping the distance between the magnetic characteristic changing portion (magnetostrictive film) and the yoke constant.

  As a means for solving the above-mentioned problems, the magnetostrictive torque sensor according to claim 1 is characterized in that a rotatable shaft and a magnet which is provided on the shaft and whose magnetic characteristics change depending on the torque applied to the shaft. A magnetostrictive torque sensor comprising: a characteristic changing unit; and a detection unit that is disposed to face the magnetic characteristic changing unit at a predetermined distance and detects a change in the magnetic characteristic of the magnetic characteristic changing unit. The portion includes a coil and a yoke that is provided around the coil and holds the coil. The yoke is urged in the axial direction by the urging means, and at the end of the yoke. The formed yoke taper surface and the fixed portion taper surface formed on the fixed portion that holds the yoke in the housing are disposed in contact with each other.

According to the first aspect of the magnetostrictive torque sensor of the present invention, since the yoke is urged in the axial direction by the urging means, the yoke taper surface is the fixed portion taper surface of the fixed portion that holds the yoke in the housing. Always abut.
For this reason, even if the housing or the like thermally expands due to a temperature change, the fixed portion taper surface of the fixed portion is always pressed against the yoke taper surface of the yoke by the urging means. The pressure from can be made substantially constant. Therefore, the magnetic characteristics of the yoke can be stabilized. As a result, output characteristics can be stabilized. Also, rattling can be eliminated. As a result, it is possible to eliminate the change in the magnetic flux due to the relative position fluctuation between the yoke and the magnetostrictive film.

  The magnetostrictive torque sensor according to claim 2 is the magnetostrictive torque sensor according to claim 1, wherein the magnetic characteristic changing portion and the yoke are provided via a predetermined gap in an axial direction. The yoke is held by the fixed portion disposed in the axial direction of the yoke.

According to the magnetostrictive torque sensor of the present invention, the magnetic characteristic changing portion and the yoke are provided with a predetermined gap in the axial direction, and the yoke is provided with fixed portion taper surfaces at both ends in the axial direction. Is held by a fixed portion. For this reason, even if the housing expands due to thermal expansion, the fixed portion taper surface of the fixed portion is always in pressure contact with the yoke taper surface, so that the gap is eliminated and the magnetic property changing portion and each yoke are not in contact with each other. The magnetic properties of the are constant.
As a result, the output of the magnetostrictive torque sensor becomes unstable due to temperature and expansion, and the output can be stabilized.

  A magnetostrictive torque sensor according to a third aspect of the present invention is the magnetostrictive torque sensor according to the second aspect, wherein the yoke tapered surface formed between the yokes contacts the fixed portion tapered surface. The fixed portion is interposed in a contact state, and the yoke, the fixed portion, and the biasing means are formed in the housing in a state where adjacent members are in contact with each other by the spring force of the biasing means. It is housed in the sensor housing part.

  According to the third aspect of the magnetostrictive torque sensor of the present invention, the yoke, the fixing portion, and the urging means housed in the sensor housing portion of the housing are adjacent to each other by the spring force of the urging means. Are stored without rattling in a state where they are in contact with each other.

  A magnetostrictive torque sensor according to a fourth aspect of the present invention is the magnetostrictive torque sensor according to any one of the first to third aspects, wherein the motor is driven in accordance with the steering torque to switch the vehicle. The present invention is characterized in that it is applied to an electric power steering device that steers.

  According to the magnetostrictive torque sensor of the fourth aspect of the present invention, the magnetostrictive torque sensor is used as a sensor for detecting the steering torque of the electric power steering device. However, it is possible to provide an electric power steering device that can maintain good steering feeling without being affected by rattling even when it is affected by temperature, thermal expansion, or vibration from the road surface.

  According to the magnetostrictive torque sensor of the present invention, even if the housing or the like is thermally expanded due to the outside air temperature, frictional heat, or the like, the magnetic characteristic change is caused by bringing the yoke taper surface and the fixed portion taper surface into contact with each other by the biasing means. The output can be stabilized by making the magnetic characteristics between the portion (magnetostrictive film) and the yoke constant.

Next, an example of a magnetostrictive torque sensor according to an embodiment of the present invention will be described with reference to FIGS.
The magnetostrictive torque sensor according to the present invention detects the torque that the shaft rotates by the rotational force acting on the shaft. Hereinafter, as an example of the embodiment of the present invention, the steering torque in the electric power steering apparatus is calculated. The case of detection will be described as an example.
First, prior to describing a magnetostrictive torque sensor according to an embodiment of the present invention, an electric power steering apparatus for a vehicle in which the magnetostrictive torque sensor is mounted will be described.
The magnetostrictive torque sensor changes in the vertical and horizontal directions depending on the installation direction, and will be described with the upper side of the drawing as the upper direction.
FIG. 1 is a schematic diagram showing an electric power steering apparatus including a magnetostrictive torque sensor according to an embodiment of the present invention.

≪Configuration of electric power steering device≫
As shown in FIG. 1, the electric power steering apparatus 11 is the same as the electric power steering apparatus 101 provided with the magnetostrictive torque sensor 103 shown in FIGS. 6 and 7 described in the prior art, except for the magnetostrictive torque sensor 1. It has become a structure.
That is, the electric power steering device 11 shown in FIG. 1 includes a magnetostrictive torque sensor 1 that detects a steering torque input from a handle 12 by a driver, and a motor 14 that applies an auxiliary steering force to the driver's steering. A reduction device 15 that increases the rotational torque of the motor 14, an ECU (Electrical Control Unit) 17 that drives and controls the motor 14 according to detection signals from the magnetostrictive torque sensor 1 and the vehicle speed sensor 16, A rack shaft 19 and a pinion gear 41 that change the direction of the tire 18 by transmitting the rotation to the tires 18 and 18 are mainly configured.

≪Configuration of magnetostrictive torque sensor≫
FIG. 2 is a schematic cross-sectional view of the main part of the electric power steering apparatus showing the installation state of the magnetostrictive torque sensor according to the embodiment of the present invention.
As shown in FIG. 2, the magnetostrictive torque sensor 1 includes a shaft 4 rotatably supported by a bearing 3 on a sensor housing case 2, a magnetic characteristic changing portion 5 provided on the shaft 4, and the magnetic characteristics. The change unit 5 includes a detection unit 7 that is arranged to face the magnetic property change unit 5 with a predetermined distance from the magnetic property change unit 5 and detects a torque applied to the shaft 4.
Hereinafter, the embodiment of the present invention will be described by taking the case of the magnetostrictive torque sensor 1 including the magnetostrictive films 51 and 52, the coils 71 and 72, and the yokes 73 and 74 as an example.

  When the steering torque from the handle 12 (see FIG. 1) acts on the shaft 4, the magnetostrictive torque sensor 1 changes the magnetic characteristics of the magnetostrictive films 51 and 52 according to the twist generated in the shaft 4. The direction and the magnitude of the steering torque applied to the shaft 4 are detected by electrical detection using, for example.

<Configuration of sensor housing case>
The sensor housing case 2 is a case for housing the magnetostrictive torque sensor 1 and the like, and includes an upper case portion 21 disposed on the upper side and a lower case portion that is bolted to match the lower side of the upper case portion 21. 22.

The upper case portion 21 is a case having a sensor housing portion 21b for housing the yokes 73 and 74, the holding member (fixed portion) 8 and the like, and a shaft hole 21a through which the shaft 4 is inserted. The upper case portion 21 maintains the airtightness in the sensor housing case 2 by disposing the sealing material 10 in the shaft hole 21a.
The sensor storage part 21b has a cylindrical space having a shaft hole 21a at the upper end and an opening 21c at the lower end. A yoke 73, a holding member 8, a yoke 74, and a leaf spring 6 are inserted into the sensor storage portion 21b in this order from the opening 21c side, and the circlip 9 is mounted in the opening 21c. Are housed in a state of elastic contact with each other.

  The lower case portion 22 is a case for housing the bearing 3 and the pinion gear 41. In addition, the lower case portion 22 is provided with a motor 14 (see FIG. 1), a reduction gear 15 (see FIG. 1), a rack shaft 19 and the like.

<Configuration of shaft>
As shown in FIG. 1, the shaft 4 is a steering shaft that is connected to the handle 12 via universal joints 13 and 13 and rotates together with the handle 12. As shown in FIG. 2, the shaft 4 is integrally provided with a pinion gear 41 at the lower end, and is housed in the sensor housing case 2 so as to be rotatable in the vertical direction with bearings 31 and 32 interposed therebetween. . On the outer peripheral surface of the shaft 4 facing the coils 71 and 72, the magnetostrictive films 51 and 52 of the magnetic characteristic changing portion 5 are disposed at two locations. The upper end portion of the shaft 4 is provided in a state of protruding from the sensor housing case 2 through the shaft hole 21 a of the upper case portion 21 and the ring-shaped sealing material 10.

  The shaft 4 is formed using, for example, a chromium molybdenum steel material (for example, SCM822) or the like. The shaft 4 is subjected to a heat treatment such as quenching on the chromium molybdenum steel material in advance, and then the magnetostrictive films 51 and 52 are deposited by using a PVD method such as sputtering or ion plating, a plating method, a plasma spraying method, or the like. is doing. The Rockwell hardness of the shaft 4 is desirably set within the range of HRC 40 to 65.

<Bearing configuration>
As shown in FIG. 2, the bearing 3 is a member that pivotally supports the shaft 4 and includes, for example, a plurality of bearings 31 and 32. The bearings 31 and 32 are, for example, ball bearings or roller bearings, and are mounted in the lower case portion 22 so as to pivotally support the lower end portion of the shaft 4 and the upper shaft 4 of the pinion gear 41.

<Configuration of magnetic property changing section>
The magnetic characteristic changing unit 5 changes the magnetic characteristics (permeability) of the magnetostrictive films 51 and 52 by strain generated by applying a steering torque to the shaft 4, and the outer peripheral surface (outer surface) of the shaft 4. In addition, a plurality of magnetostrictive films 51 and 52 are arranged in the axial direction at predetermined intervals.
The magnetostrictive films 51 and 52 are integrally fixed to the shaft 4 by plating or vapor deposition of a magnetostrictive material made of, for example, an Fe—Ni based or Fe—Cr based alloy film. The magnetostrictive films 51 and 52 are made of a magnetostrictive material having anisotropy in opposite directions.

<Configuration of detection unit>
The detector 7 detects the steering torque of the shaft 4 by electrically detecting the magnetic characteristics of the magnetostrictive films 51 and 52. The detection unit 7 includes a plurality of coils 71 and 72 and yokes 73 and 74 provided around the coils 71 and 72 and holding the coils 71 and 72.
As shown in FIG. 1, the detection unit 7 is electrically connected to the ECU 17 via detection circuits 75 and 76 that detect torque detection voltages transmitted when the coils 71 and 72 are alternately energized in accordance with changes in magnetostriction characteristics. It is connected to the.

FIG. 3 is an enlarged view of a main part of the magnetostrictive torque sensor shown in FIG.
<Configuration of coil>
As shown in FIG. 3, the coils 71 and 72 energize the magnetostrictive films 51 and 52 to detect a change in permeability, which is a magnetostrictive characteristic of the magnetostrictive films 51 and 52, when a steering torque is input. Consists of. The coils 71 and 72 are provided on the inner peripheral side of the upper case portion 21 so as to be separated from each other in the vertical direction, and are detection means for detecting steering torque. The coils 71 and 72 are wound around a bobbin (not shown) and are provided in the yokes 73 and 74, and are arranged to face the magnetostrictive films 51 and 52 with a predetermined distance b therebetween.

<Composition of the yoke>
As shown in FIG. 3, the yokes 73 and 74 are members constituting the outer frame of the coils 71 and 72, and are made of annular members having a substantially U-shaped cross section. The yokes 73 and 74 are made of, for example, a soft magnetic steel plate. The yokes 73 and 74 are formed with yoke taper surfaces 73a, 73b, 74a, and 74b that are chamfered at about 45 degrees at upper and lower outer peripheral ends, respectively. In the axial direction of the shaft 4 between the yokes 73 and 74, a holding member 8 having fixed portion tapered surfaces 8a and 8b of about 45 degrees is interposed at the upper and lower outer peripheral ends, and there is a predetermined gap c.
The angles of the yoke taper surfaces 73a, 73b, 74a, 74b and the fixed portion taper surfaces 8a, 8b are not limited to 45 degrees and can be changed as appropriate, for example, 30 degrees, 60 degrees, etc. There may be.

The yokes 73 and 74 are inserted into the sensor housing portion 21b from the opening 21c in the order of the upper yoke 73, the holding member 8, the lower yoke 74, and the leaf spring 6 so as to be freely movable in the axial direction. The clip 9 is assembled in the sensor housing case 2 by fixing it to the inner wall of the sensor housing portion 21b.
Thus, the yokes 73 and 74 disposed in the sensor storage portion 21b are axially (in the direction of arrow A) by the leaf spring (biasing means) 6 disposed below the lower yoke 74. Are formed on the yoke taper surfaces 73b and 74a formed on the outer peripheral ends of the yokes 73 and 74 and the holding member (fixed portion) 8 for holding the yokes 73 and 74 on the upper case portion (housing) 21. The fixed portion taper surfaces 8a and 8b are provided so as to come into contact with each other.

<Configuration of holding member (fixed portion)>
As shown in FIG. 3, the holding member 8 is a member that is interposed between the upper yoke 73 and the lower yoke 74 and is disposed so as to always maintain a predetermined distance between the yokes 73 and 74. is there. The holding member 8 is formed of, for example, an annular member having a substantially right-angled cross section, and fixed portion taper surfaces 8a and 8b that are in pressure contact with the yoke taper surfaces 73b and 74a on the inner surface upper side and the inner surface lower side (at both ends in the axial direction). Is formed.

<Configuration of leaf spring (biasing means)>
As shown in FIG. 3, the leaf spring 6 is made of, for example, a metal such as spring steel having a spring property in the axial direction, which is an annular corrugated leaf spring. The leaf spring 6 is a spring member for urging the yokes 73 and 74 in the axial direction with the shaft hole 21 a, and is interposed between the lower yoke 74 and the circlip 9, for example. The leaf springs 6 arranged in this way are arranged adjacent to each other by pressing the yoke 73, the holding member 8 and the yoke 74 arranged in series in the axial direction upward in the sensor housing portion 21b. The members are assembled so that the members are pressed against each other.
The leaf spring 6 corresponds to “biasing means” described in the claims.

<Circlip configuration>
The circlip 9 is a member for preventing the leaf spring 6, the yokes 73 and 74, and the holding member 8 from being detached from the sensor storage portion 21b. The circlip 9 is attached to the inner wall of the opening 21c in a state where the leaf spring 6 accommodated in the sensor accommodating portion 21b is compressed.

≪Operation of magnetostrictive torque sensor≫
Next, the operation of the magnetostrictive torque sensor 1 will be described with reference to FIGS.
As shown in FIG. 1, in the electric power steering apparatus 11, the steering torque when the driver operates the steering wheel is detected using the magnetostrictive torque sensor 1, and a detection signal from the magnetostrictive torque sensor 1 is detected by the ECU 17. The motor 14 is driven and controlled in accordance with a detection signal from the vehicle speed sensor 16, and the torque of the motor 14 at this time is increased by the speed reducer 15 and transmitted to the tires 18 and 18 through the pinion gear 41 and the rack shaft 19. Yes.

  As shown in FIG. 3, in the magnetostrictive torque sensor 1, the yoke 73, the holding member 8, the yoke 74, and the leaf spring 6 are inserted into the sensor housing portion 21b in this order from the opening 21c side, and the circlip 9 is By mounting near the opening end in the opening 21c, the members are assembled in a state of elastic contact with each other.

  Therefore, the leaf spring 6 presses the lower yoke 74, so that the yoke taper surface 74 a of the lower yoke 74 presses the lower fixed portion taper surface 8 b of the holding member 8, and this holding member. The upper fixed portion taper surface 8a of the upper 8 presses the lower yoke taper surface 73b of the upper yoke 73, and the upper surface of the upper yoke 73 presses the upper inner wall 21d of the sensor storage portion 21b. The members housed inside are biased so as to come into contact with each other.

More specifically, as shown in FIG. 3, the leaf spring 6 presses the circlip 9 in the downward direction of the arrow B and presses the lower yoke 74 in the upward direction of the arrow A.
When the lower yoke 74 is pressed upward by the leaf spring 6, the upper yoke taper surface 74 a presses the lower fixed portion taper surface 8 b of the holding member 8 diagonally upward by the arrow C. To do. For this reason, the annular lower yoke 74 is moved in the direction of arrow D (the axial center line direction of the shaft 4) by the reaction force (force in the direction opposite to the arrow C) of the fixed portion taper surface 8b of the annular holding member 8. It is pushed and brought closer to the rotation center side of the shaft 4. As a result, the space b between the lower yoke 72 and the magnetostrictive film 52 disposed on the surface of the shaft 4 is constant, and the rattling is eliminated.

  The annular holding member 8 is pressed in the direction of arrow C by the upper yoke taper surface 74a of the lower yoke 74, thereby pressing the inner side wall 21e of the sensor storage portion 21b in the outer direction of arrow E. The wall 21e is moved in the direction of arrow G. Then, the holding member 8 presses the upper yoke 73 in the oblique direction of the arrow F by the upper fixed portion tapered surface 8a.

When the yoke taper surface 73b is pressed in the direction of the arrow F by the holding member 8, the annular upper yoke 73 moves upward in the direction of the arrow I and presses the inner wall 21e. The shaft 4 is pressed toward the center of rotation of the shaft 4.
For this reason, the space | interval b with the magnetostrictive film 51 arrange | positioned on the surface of the shaft 4 becomes constant, and the upper yoke 73 does not rattle.
As a result, the output is stabilized. Moreover, even if it receives vibration, the magnetostrictive torque sensor 1 can maintain good detection accuracy of the steering torque.

The detection unit 7 of the magnetostrictive torque sensor 1 configured as described above is set at a predetermined interval b so that a gap in the radial direction between the magnetostrictive films 51 and 52 and the yokes 73 and 74 is appropriate at low temperatures. Yes.
For example, when the temperature is low, the sensor housing case 2 contracts to about twice the contraction magnitude of the yokes 73 and 74, but is allowed by the spring force of the leaf spring 6. Further, even when the sensor housing case 2 expands with respect to the yokes 73 and 74 at a high temperature, it is allowed by the spring force of the leaf spring 6.

  That is, the detecting portion 7 of the magnetostrictive torque sensor 1 is always brought close to the upper inner wall 21d side of the sensor housing portion 21b by the spring force of the leaf spring 6 with the yoke 74, the holding member 8 and the yoke 73 pressed against each other. At the same time, the yokes 73 and 74 are brought close to the rotation center side of the shaft 4 and held in a stable state. As a result, the pre-pressure of the yokes 73 and 74 does not change with temperature and is kept constant, so that the magnetic characteristics of the yokes 73 and 74 can be kept constant and the output can be stabilized.

  In addition, since the magnetostrictive torque sensor 1 is applied to the electric power steering apparatus 11 that applies an auxiliary steering force to the steering mechanism of the automobile, the magnetostrictive torque sensor can be used even if it receives a change in temperature or vibration of the automobile. 1, the detection accuracy of the steering torque can be increased, and the performance, reliability, and the like of the electric power steering device 11 can be improved.

  The present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the technical idea. The present invention extends to these modifications and changes. Of course.

≪Modification≫
Next, a modification of the present invention will be described with reference to FIGS.
In addition, in a modification, description of the member which has the same function as the magnetostrictive torque sensor 1 which concerns on the said embodiment shown in FIGS. 1-3 is abbreviate | omitted.
FIG. 4 is a view showing a modification of the magnetostrictive torque sensor according to the embodiment of the present invention, and is a schematic cross-sectional view of the main part of the electric power steering apparatus showing the installation state of the magnetostrictive torque sensor. FIG. 5 is an enlarged view of a main part of the magnetostrictive torque sensor shown in FIG.

  The leaf spring 6 (see FIGS. 1 to 3) provided in the magnetostrictive torque sensor 1 of the above embodiment is arranged on the upper side like the leaf spring 6A of the magnetostrictive torque sensor 1A of the modification shown in FIGS. It is disposed between the yoke 73A and the lower yoke 74A so as to press the upper yoke 73A upward in the direction of the arrow J and press the lower yoke 74A downward in the direction of the arrow K. May be.

  In this case, an annular holding member 8A having a fixed portion taper surface 8Aa that presses against the yoke taper surface 74Ab of the lower yoke 74A is disposed on the opening 21c side of the sensor storage portion 21b. A yoke 73A, a leaf spring 6A, a yoke 74A, a holding member 8A, and a bearing 34 are inserted into the sensor storage portion 21b in order from the opening 21c, and an annular fixing screw 9A is fixed to the opening 21c.

  Even in this case, the upper yoke 73A is always assembled in a state of being pressed against the upper inner wall 21d of the sensor housing portion 21b by being pressed by the leaf spring 6A, and the lower yoke 74A is also attached to the plate. By pressing the spring 6A, the yoke taper surface 74Ab is always assembled in a state of being pressed against the fixed portion taper surface 8Aa of the holding member 8A, and is held without rattling.

  The holding member 8A is formed of an annular member having a fixed portion tapered surface 8Aa at the upper inner peripheral end, and the upper end surface comes into contact with the stepped portion 21f formed in the vicinity of the opening 21c of the sensor housing portion 21b. Are fixed by fixing screws 9A. The fixing screw 9A is screwed to the female screw portion formed in the opening 21c.

  Thus, in the modified example of the present invention, the holding member 8A is fixed by the step portion 21f of the sensor housing portion 21b and the fixing screw 9A, so that the yokes 73A and 74A can be held firmly. .

  Further, the yokes 73A and 74A have a two-layer structure in which a cross section is formed in an approximately E shape and two coils 71A and 72A are provided. Thus, the yokes 73A and 74A may be outer frames of a coil unit in which the coils 71A and 72A are provided in a plurality of layers. Further, the yoke 73A may be divided to form a multi-layer coil unit.

≪Other variations≫
The leaf spring 6 shown in FIGS. 2 and 3 urges the yokes 73 and 74 housed in the sensor housing portion 21b to rattle, the gap between the yokes 73 and 74 and the holding member 8, and the holding member. 8 may be an elastic material for eliminating a gap between the sensor 8 and the inner wall of the sensor storage portion 21b. For example, the leaf spring 6 may be a flat spring, a spring washer, a cylindrical coil spring, a conical coil spring, an annular member integrally formed with an elastic piece, a member made of a rubber material, etc. It is not limited.

  The leaf spring 6 may be assembled so as to urge the yokes 73 and 74 in the axial direction. For example, the installation position of the leaf spring 6 may be between the upper yoke 73 and the upper inner wall of the sensor storage portion 21b, and the installation position is not particularly limited.

  Further, although the magnetostrictive torque sensor 1 has been described as an example in which the magnetostrictive torque sensor 1 is applied to an electric power steering apparatus 11 that drives a motor in accordance with steering torque to steer the vehicle, other than that, a torsion bar of an automobile It may also be applied to other various devices.

It is a mimetic diagram showing an electric power steering device provided with a magnetostriction type torque sensor concerning an embodiment of the present invention. It is a principal part schematic sectional drawing of the electric power steering device which shows the installation state of the magnetostrictive torque sensor which concerns on embodiment of this invention. It is a principal part enlarged view of the magnetostrictive torque sensor shown in FIG. It is a figure which shows the modification of the magnetostrictive torque sensor which concerns on embodiment of this invention, and is a principal part schematic sectional drawing of the electric power steering apparatus which shows the installation state of a magnetostrictive torque sensor. It is a principal part enlarged view of the magnetostrictive torque sensor shown in FIG. It is a schematic diagram which shows the conventional electric power steering apparatus. It is principal part sectional drawing which shows the installation state of the magnetostrictive torque sensor in the conventional electric power steering apparatus.

Explanation of symbols

1,1A Magnetostrictive torque sensor 2 Sensor housing case (housing)
3 Bearing 4 Shaft 5 Magnetic property changing part 6, 6A Leaf spring (biasing means)
7, 7A detection part 8, 8A holding means (fixing part)
8a, 8b, 8Aa Fixed portion taper surface 11 Electric power steering device 14 Motor 21 Upper case portion (housing)
21b Sensor accommodating portion 71, 72, 71A, 72A Coil 73, 74, 73A, 74A Yoke 73a, 73b, 74a, 74b, 74Ab Yoke taper surface b, c Predetermined gap

Claims (4)

A rotatable shaft,
A magnetic property changing portion that is provided on the shaft and changes magnetic properties by torque applied to the shaft;
In a magnetostrictive torque sensor including a detection unit that is disposed to face the magnetic characteristic change unit at a predetermined distance and detects a change in the magnetic characteristic of the magnetic characteristic change unit.
The detection unit includes a coil and a yoke that is provided around the coil and holds the coil.
The yoke is urged in the axial direction by the urging means, and the yoke taper surface formed at the end of the yoke and the fixed portion taper surface formed at the fixed portion that holds the yoke in the housing are in contact with each other. A magnetostrictive torque sensor characterized by being disposed in contact with each other. The magnetic property changing portion and the yoke are provided via a predetermined gap in the axial direction,
The magnetostrictive torque sensor according to claim 1, wherein the yoke is held by the fixed portion disposed in the axial direction of the yoke. Between the yokes, the fixed portions are interposed in a state in which the yoke tapered surfaces formed on the yokes are in contact with the fixed portion tapered surfaces,
The yoke, the fixed portion, and the biasing means are housed in a sensor housing portion formed in the housing in a state where adjacent members are in contact with each other by the spring force of the biasing means. The magnetostrictive torque sensor according to claim 2.   The magnetostrictive torque sensor according to any one of claims 1 to 3, wherein the magnetostrictive torque sensor is applied to an electric power steering device that drives a motor in accordance with steering torque to steer the vehicle.

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