JP2007240311A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further enhance the accuracy of torque detection of a torque sensor which detects a torque with coils. <P>SOLUTION: The torque sensor detects the torque acting on a rotating shaft with the coils 85, 85 arranged so as to surround the rotating shaft, and is provided with coil bobbins 84, 84 for winding the coils around and magnetic yokes for housing the coils and the coil bobbins in. The yokes comprises cup-shaped yoke bodies 88, 88, and a yoke bottom plate 89 plugging up the openings of the yoke bodies 88, 88 by fitting in the openings. Fitting-in faces 89b of the yoke bottom plate have press-fitting protrusions 89c for press-fitting in the fitting-in faces 88d, 88d. The yoke bottom plate has engaging portions 89d, 89d for performing mutual engagement with the coil bobbins, so as to regulate the shifts in the positions of the centers of the coil bobbins from the centers of the yokes. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a torque sensor that detects a torque acting on a rotating shaft with a coil.

Various types of torque sensors that detect torque acting on a rotating shaft with a coil disposed so as to surround the rotating shaft are known. Among such torque sensors, for example, a magnetostrictive torque sensor is being developed (see, for example, Patent Document 1-2).
JP 59-164932 A JP 2003-42862 A

The conventional magnetostrictive torque sensor according to Patent Document 1 and Patent Document 2 is provided with a magnetostrictive film whose magnetostrictive characteristics change according to torque on the surface of a rotating shaft, and the magnetostrictive effect generated in the magnetostrictive film is magnetically generated by a coil. It is to detect.
Such a magnetostrictive torque sensor includes a resin coil bobbin that winds a coil, and a magnetic yoke that houses the coil and the coil bobbin.

  Incidentally, the coil bobbin is a resin product while the yoke is made of a magnetic material. Since members made of different materials are combined in this way, it is necessary to take into account thermal expansion differences and dimensional tolerances. In order to absorb the difference in thermal expansion, it is conceivable to make the outer diameter of the coil bobbin slightly smaller than the inner diameter of the yoke. However, consideration must be given to prevent the displacement of the center of the coil bobbin with respect to the center of the yoke. In addition, positional displacement may occur due to external vibration. In the case of eccentricity, a gap (air gap) between the magnetostrictive film and the coil is biased, and as a result, the magnetic characteristics detected by the coil can change. For this reason, there is room for improvement in order to increase the torque detection accuracy by the torque sensor.

  An object of the present invention is to provide a technique capable of further improving the accuracy of torque detection in a torque sensor that detects torque with a coil.

  The invention according to claim 1 is a torque sensor that detects a torque acting on the rotating shaft by a coil disposed so as to surround the rotating shaft, and stores a coil bobbin around which the coil is wound, and the coil and the coil bobbin. In the torque sensor provided with a magnetic yoke, the yoke and the coil bobbin have a tapered engaging portion on at least one of the yoke and the coil bobbin so as to regulate the displacement in the radial direction and / or the axial direction. It is characterized by having.

  The invention according to claim 2 is a torque sensor that detects torque acting on the rotating shaft by a pair of coils that surround the rotating shaft and are arranged in the axial direction of the rotating shaft, and each of the pair of coils is wound. In a torque sensor including a pair of coil bobbins and a magnetic yoke that houses the pair of coils and the pair of coil bobbins, the yoke includes a flat yoke plate interposed between the pair of coil bobbins. And the pair of coil bobbins have a taper-shaped engagement portion on at least one of the yoke plate and the pair of coil bobbins so as to restrict mutual displacement in the radial direction and / or the axial direction. To do.

  According to a third aspect of the present invention, there is provided a torque sensor for detecting a torque acting on the rotating shaft by means of a coil arranged so as to surround the rotating shaft, and the coil bobbin around which the coil is wound, and the coil and the coil bobbin are accommodated. In a torque sensor provided with a magnetic yoke, the yoke or the coil bobbin has an engaging portion on at least one of the yoke and the coil bobbin so as to regulate the displacement in the radial direction and / or the axial direction. The yoke is composed of a cup-shaped yoke body and a yoke bottom plate that closes the opening by being fitted into the opening of the yoke body. At least one of the fitting surfaces of the yoke body and the yoke bottom plate is press-fitted into the mating fitting surface. It has the press-fit convex part to do.

  According to a fourth aspect of the present invention, the torque sensor according to the first, second, or third aspect is a sensor that detects a steering torque of a steering system applied to the steering handle for a vehicle, and is provided on the surface of the rotating shaft. The magnetostrictive film includes a magnetostrictive torque sensor that has a magnetostrictive film whose magnetostrictive characteristics change according to torque and detects a magnetostrictive effect generated in the magnetostrictive film with a coil.

  In the invention according to claim 1, the yoke and the coil bobbin are provided with a tapered engaging portion on at least one of the yoke and the coil bobbin so as to regulate the radial and / or axial displacement between the magnetic shield yoke and the coil bobbin. Have.

When the positional displacement in the radial direction is regulated by the tapered engaging portion, the positional displacement of the coil bobbin center relative to the center of the yoke can be regulated by the engaging portion. For this reason, the center of the coil bobbin is not shifted from the center of the yoke due to the influence of dimensional tolerance, thermal expansion, vibration and the like.
By assembling so that the center of the yoke matches the center of the rotating shaft, the center of the coil bobbin automatically matches the center of the rotating shaft. Thus, the torque sensor can be easily and accurately assembled with a simple configuration.
Moreover, even if there is a disturbance such as thermal expansion or vibration, there is no bias in the gap (air gap) between the rotating shaft and the coil. Therefore, the detection accuracy by the torque sensor can be further increased and a highly accurate state can be maintained.

Further, when the axial displacement of the coil bobbin is restricted by the tapered engaging portion, the axial displacement of the coil bobbin relative to the yoke can be restricted by the engaging portion. For this reason, the position of the coil bobbin in the axial direction can be accurately adjusted with respect to the rotation axis only by assembling the yoke with respect to the rotation axis.
Moreover, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the axial displacement of the coil with respect to the rotating shaft. Therefore, the detection accuracy by the torque sensor can be further improved, and this highly accurate state can be maintained.

Further, when both the radial displacement and the axial displacement are restricted by the tapered engaging portion, the axial displacement is also regulated in addition to the displacement of the center of the coil bobbin with respect to the yoke. be able to. For this reason, the position of the coil bobbin can be accurately adjusted with respect to the rotating shaft only by assembling the yoke with respect to the rotating shaft.
In addition, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the positional deviation in the radial direction and the axial direction of the coil with respect to the rotating shaft. Therefore, the detection accuracy by the torque sensor can be further improved, and this highly accurate state can be maintained.

  In the invention according to claim 2, the yoke plate and the pair of coil bobbins are configured such that the radial displacement and / or the axial displacement between the yoke plate interposed between the pair of coil bobbins and the pair of coil bobbins are regulated. At least one of them has a tapered engaging portion.

When the positional displacement in the radial direction is regulated by the tapered engaging portion, the positional displacement of the center of the pair of coil bobbins with respect to the center of the yoke (the center of the yoke plate) can be regulated by the engaging portion. it can. For this reason, even if it is a pair of coil bobbins, the center of a pair of coil bobbins with respect to the center of a yoke does not shift | deviate by the influence of a dimensional tolerance, thermal expansion, a vibration, etc.
By assembling so that the center of the yoke matches the center of the rotating shaft, the center of the pair of coil bobbins automatically matches the center of the rotating shaft. Thus, the torque sensor can be easily and accurately assembled with a simple configuration.
Moreover, even if there is a disturbance such as thermal expansion or vibration, there is no bias in the gap between the rotating shaft and the pair of coils. Therefore, the detection accuracy by the torque sensor can be further increased and a highly accurate state can be maintained.

In addition, when the axial displacement of the pair of coil bobbins with respect to the yoke (yoke plate) is restricted by the tapered engaging portion, the axial displacement of the pair of coil bobbins can be restricted. For this reason, the position of the coil bobbin in the axial direction can be accurately adjusted with respect to the rotation axis only by assembling the yoke with respect to the rotation axis.
Moreover, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the axial displacement of the coil with respect to the rotating shaft. Therefore, the detection accuracy by the torque sensor can be further improved, and this highly accurate state can be maintained.

Further, when both the radial displacement and the axial displacement are regulated by the tapered engaging portion, in addition to the displacement of the center of the pair of coil bobbins with respect to the yoke (yoke plate), the axial displacement Misalignment can also be regulated. For this reason, the position of the pair of coil bobbins can be accurately aligned with respect to the rotation shaft only by assembling the yoke with respect to the rotation shaft.
In addition, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the positional deviation in the radial direction and the axial direction of the pair of coils with respect to the rotating shaft. Therefore, the detection accuracy by the torque sensor can be further improved, and this highly accurate state can be maintained.

  In the invention according to claim 3, at least one of the yoke and the coil bobbin has an engaging portion so as to restrict the radial and / or axial displacement between the magnetic shield yoke and the coil bobbin. Yes.

When the mutual displacement in the radial direction is restricted by the engaging portion, the displacement in the center of the coil bobbin with respect to the center of the yoke can be restricted by the engaging portion. For this reason, the center of the coil bobbin is not shifted from the center of the yoke due to the influence of dimensional tolerance, thermal expansion, vibration and the like.
By assembling so that the center of the yoke matches the center of the rotating shaft, the center of the coil bobbin automatically matches the center of the rotating shaft. Thus, the torque sensor can be easily and accurately assembled with a simple configuration.
Moreover, even if there is a disturbance such as thermal expansion or vibration, there is no bias in the gap (air gap) between the rotating shaft and the coil. Therefore, the detection accuracy by the torque sensor can be further increased and a highly accurate state can be maintained.

In addition, when the axial displacement of the coil bobbin is restricted by the engaging portion, the axial displacement of the coil bobbin with respect to the yoke can be restricted by the engaging portion. For this reason, the position of the coil bobbin in the axial direction can be accurately adjusted with respect to the rotation axis only by assembling the yoke with respect to the rotation axis.
Moreover, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the axial displacement of the coil with respect to the rotating shaft. Therefore, the detection accuracy by the torque sensor can be further improved, and this highly accurate state can be maintained.

Further, when both the radial and axial displacements are regulated by the engaging portion, in addition to the positional deviation at the center of the coil bobbin with respect to the yoke, axial displacement can also be regulated. . For this reason, the position of the coil bobbin can be accurately adjusted with respect to the rotating shaft only by assembling the yoke with respect to the rotating shaft.
In addition, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the positional deviation in the radial direction and the axial direction of the coil with respect to the rotating shaft. Therefore, the detection accuracy by the torque sensor can be further improved, and this highly accurate state can be maintained.

Further, in the invention according to claim 3, when the yoke bottom plate is fitted to close the opening of the cup-shaped yoke main body, the press-fitting convex portion provided on the fitting surface of the yoke main body and / or the yoke bottom plate is not provided. By press-fitting into the fitting surface, the yoke bottom plate can be fixed to the yoke body.
When the yoke bottom plate is fitted into the yoke body, the press-fitting convex portion is press-fitted only into a part of the fitting surface. For this reason, the press-fitting force can be small. The stress generated by the press fitting can be reduced. By reducing the stress, it is possible to suppress variation in magnetic permeability in the yoke. As a result, variation in output characteristics of the torque sensor can be suppressed.

  In the invention according to claim 4, the torque sensor is constituted by a magnetostrictive torque sensor, and the magnetostrictive torque sensor detects the steering torque of the steering system applied to the steering handle for the vehicle. It can be detected accurately over a long period of time. By mounting such a high-accuracy magnetostrictive torque sensor in a vehicular electric power steering apparatus, it is possible to perform steering torque control with an enhanced steering feeling (steering feeling) based on more accurate steering torque. .

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. Hereinafter, an example in which the torque sensor is mounted on the electric power steering apparatus will be described.

  FIG. 1 is a schematic diagram of an electric power steering apparatus according to the present invention. The electric power steering apparatus 10 includes a steering system 20 that extends from a steering handle 21 of a vehicle to steering wheels (front wheels) 29 and 29 of the vehicle, and an auxiliary torque mechanism 40 that applies an auxiliary torque to the steering system 20.

The steering system 20 is connected to the steering handle 21 via the steering shaft 22 and the universal shaft joints 23 and 23, one end 24 a of the pinion shaft 24 (that is, the rotating shaft 24), and racked to the other end 24 b of the pinion shaft 24. A rack shaft 26 is connected via an and pinion mechanism 25, and left and right steering wheels 29, 29 are connected to both ends of the rack shaft 26 via left and right tie rods 27, 27 and knuckles 28, 28.
The rack and pinion mechanism 25 includes a pinion 31 formed on the pinion shaft 24 and a rack 32 formed on the rack shaft 26.

  According to the steering system 20, when the driver steers the steering handle 21, the steering wheels 29 and 29 can be steered via the rack and pinion mechanism 25 by the steering torque.

The auxiliary torque mechanism 40 detects the steering torque of the steering system 20 applied to the steering handle 21 with the torque sensor 41, generates a control signal with the control unit 42 based on this detection signal, and responds to the steering torque based on this control signal. The auxiliary torque is generated by the electric motor 43, the auxiliary torque is transmitted to the pinion shaft 24 via the worm gear mechanism 44, and the auxiliary torque is transmitted from the pinion shaft 24 to the rack and pinion mechanism 25 of the steering system 20. Mechanism.
According to the electric power steering apparatus 10, the steering wheels 29 and 29 can be steered by the rack shaft 26 by a combined torque obtained by adding the auxiliary torque of the electric motor 43 to the steering torque of the driver.

FIG. 2 is an overall configuration diagram of the electric power steering apparatus according to the present invention, in which the left end portion and the right end portion are cut away. This figure shows that the rack shaft 26 of the electric power steering apparatus 10 is accommodated in a housing 51 extending in the vehicle width direction (left-right direction in FIG. 2) so as to be slidable in the axial direction.
The rack shaft 26 is a shaft in which tie rods 27 and 27 are connected to both longitudinal ends protruding from the housing 51 via ball joints 52 and 52. 53 and 53 are dust seal boots.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2 and shows a vertical cross-sectional structure of the electric power steering apparatus 10. FIG. 4 is an enlarged view around the torque sensor shown in FIG.
As shown in FIG. 3, the electric power steering apparatus 10 houses a pinion shaft 24, a rack and pinion mechanism 25, a torque sensor 41 and a worm gear mechanism 44 in a housing 51, and the upper opening of the housing 51 is closed by an upper housing 54. It is a thing. Hereinafter, the term “housing 51” includes the upper housing 54.

  The electric motor 43 has a motor shaft that extends horizontally from the other side of the paper into the front housing 51. The motor shaft is an output shaft connected to the worm shaft 46 of the worm gear mechanism 44. The worm shaft 46 includes a worm 47 formed integrally. The housing 51 rotatably supports both ends of the worm shaft 46 extending horizontally through bearings.

  The worm gear mechanism 44 is configured to transmit torque from the worm 47 to the load side via the torque transmission worm wheel 48 by meshing the drive side worm 47 with the torque transmission worm wheel 48. Further, the worm gear mechanism 44 includes an auxiliary worm wheel 49 in addition to the torque transmitting worm wheel 48. The auxiliary worm wheel 49 is an auxiliary gear provided to remove backlash between the worm 47 and the torque transmitting worm wheel 48.

As shown in FIGS. 1 and 3, one end portion 24 a of the pinion shaft 24 (rotating shaft 24) is a shaft end portion connected to the steering handle 21 via the universal shaft joints 23 and 23 and the steering shaft 22. The one end 24a has a serration 24c for connecting the universal shaft joint 23 to the shaft end. The center line CL2 of the universal shaft joint 23 connected to the one end 24a of the pinion shaft 24 is inclined by an angle θ1 (hereinafter referred to as “inclination angle θ1”) with respect to the center line CL1 of the pinion shaft 24. .
On the other hand, the other end 24 b of the pinion shaft 24 is a shaft end portion connected to the steering wheel 29 via the rack and pinion mechanism 25.

  As shown in FIG. 3, the pinion shaft 24 is supported by the housing 51 only through the three bearings 55 to 57 except for the one end 24 a. That is, the pinion shaft 24 includes a torque transmission worm wheel 48 in the central portion of the longitudinal axis, and includes magnetostrictive portions 81 and 82 of the torque sensor 41 on one end side (one end portion 24a) from the central portion of the longitudinal axis. The pinion 31 is provided on the other end side (the other end portion 24b) from the portion.

  The pinion shaft 24 has (1) the shaft end position of the other end 24b via the first bearing 55, and (2) the position between the pinion 31 and the torque transmission worm wheel 48 via the second bearing 56. (3) The position between the torque transmitting worm wheel 48 and the magnetostrictive portions 81, 82 is rotatably supported by the housing 51 via the third bearing 57. These three bearings 55 to 57 are rolling bearings such as ball bearings. The pinion shaft 24 is restricted from moving in the axial direction with respect to the housing 51.

  Here, the one end portion 24 a of the pinion shaft 24 refers to the serration 24 c side with respect to the third bearing 57. Since the one end 24a is not supported by the three bearings 55 to 57, it can be said that it is basically a free end.

  Incidentally, as shown in FIGS. 3 and 4, the vicinity of the magnetostrictive portions 81 and 82 in the one end portion 24 a of the pinion shaft 24 is supported by a free end bearing 61. The free end bearing 61 is called a free end bearing because it is a bearing that supports the one end 24a, which is a free end. The support structure by the free end bearing 61 will be described below.

  5 (a) and 5 (b) are a sectional view and an operation view around the free end bearing and the elastic body shown in FIG. As shown in FIGS. 4 and 5A, the free end bearing 61 is a rolling bearing such as a ball bearing. The free end bearing 61 is supported by the housing 51 via an elastic body 63.

More specifically, one end 24a can be rotatably supported by the free end bearing 61 by fitting the two magnetostrictive portions 81 and 82 of the pinion shaft 24 into the free end bearing 61. .
The free end bearing 61 is mounted in an annular bearing holding member 62 with its relative rotation and axial movement restricted. The bearing holding member 62 has an annular groove 62b on the outer peripheral surface 62a, and an annular elastic body 63 is attached to the groove 62b by fitting. The elastic body 63 is made of a material having a predetermined flexibility such as rubber, and is made of, for example, an O-ring.

  Such a bearing holding member 62 is housed in the housing 51 with its axial movement restricted. The outer diameter D2 of the bearing holding member 62 is set smaller than the inner diameter D1 of the housing 51. For this reason, a gap Ag having a dimension δ is provided between the inner surface 51 a of the housing 51 and the outer peripheral surface 62 a of the bearing holding member 62. When the bearing holding member 62 is fitted into the housing 51, the outer peripheral surface of the elastic body 63 is in a state of being substantially in contact with the inner surface 51 a of the housing 51.

  The one end 24a of the pinion shaft 24 can be displaced in the radial direction by the dimension δ of the gap Ag. That is, when the pinion shaft 24 is bent, the elastic body 63 can be elastically deformed according to the force acting in the radial direction. As a result, as shown in FIG. 5B, the housing 51 can be displaced until it contacts the inner surface 51 a of the housing 51 and the outer peripheral surface 62 a of the bearing holding member 62. At this time, the center line CL1 of the pinion shaft 24 is eccentric by the dimension δ.

  As shown in FIG. 3, the housing 51 includes an oil seal 58 and a rack guide 70. The rack guide 70 includes a guide portion 71 that contacts the rack shaft 26 from the opposite side of the rack 32, an adjustment bolt 73 that pushes the guide portion 71 through the compression spring 72, a contact member 74 that slides the back surface of the rack shaft 26, It consists of a lock nut 75 for positioning the adjustment bolt 73.

As shown in FIGS. 3 and 4, the torque sensor 41 is provided on the surface of the pinion shaft 24 and one end portion 24a of the pinion shaft 24, and a pair of upper and lower magnetostrictive portions 81 whose magnetostrictive characteristics change according to torque, 82 and a magnetostrictive torque sensor that is arranged in the vicinity of the magnetostrictive portions 81 and 82 and includes coils 85 and 85 that detect the magnetostrictive effect generated in the magnetostrictive portions 81 and 82.
In other words, the torque sensor 41 includes a pair of magnetostrictive portions 81 and 82 provided on the pinion shaft 24 and a pair of detection portions 83 and 83 provided around the magnetostrictive portions 81 and 82.

  As shown in FIG. 4, the magnetostrictive portions 81 and 82 are made of a magnetostrictive film in which residual strains in opposite directions are given to the longitudinal direction of the pinion shaft 24. The magnetostrictive films 81 and 82 are films made of a material having a large change in magnetic flux density with respect to a change in strain. For example, the magnetostrictive films 81 and 82 are Ni—Fe alloy films formed on the outer peripheral surface of the pinion shaft 24 by vapor phase plating. is there. The thickness of this alloy film is desirably about 5 to 20 μm. The thickness of the alloy film may be less than or greater than this. The magnetostriction direction of the second magnetostrictive film 82 is different from the magnetostriction direction of the first magnetostrictive film 81 (has magnetostriction anisotropy). The two magnetostrictive films 81 and 82 are arranged with a predetermined interval in the axial longitudinal direction.

  Ni-Fe-based alloy films tend to increase the magnetostriction effect when the Ni content is approximately 20% by weight and approximately 50% by weight, so that the magnetostriction effect tends to increase. Is preferably used. For example, as the Ni—Fe-based alloy film, a material containing 50 to 60% by weight of Ni and the rest being Fe is used. The magnetostrictive films 81 and 82 may be ferromagnetic films, such as permalloy (Ni; about 78 wt%, Fe; remaining) or supermalloy (Ni; 78 wt%, Mo; 5 wt%, Fe; remaining). ). Here, Ni is nickel, Fe is iron, and Mo is molybdenum.

  As shown in FIG. 4, the pair of detection units 83 and 83 electrically detect the magnetostriction effect generated in the magnetostriction units 81 and 82 and output the detection signal as a torque detection signal. It is stored in. Hereinafter, the detection units 83 and 83 will be described in detail.

  First, a first embodiment of the detection unit 83 will be described with reference to FIGS. 4 and 6 to 8. FIG. 6 is a cross-sectional view of the detecting portion (first embodiment) of the torque sensor according to the present invention. FIG. 7 is an enlarged view of the detection unit (first embodiment) shown in FIG. FIG. 8 is a view taken along line 8-8 in FIG.

  4, 6, and 7, the detection unit 83 of the first embodiment includes a pair of upper and lower cylindrical (substantially annular) coil bobbins 84 and 84 that are passed through the pinion shaft 24, and a coil bobbin 84, 84, coils 85 and 85 wound around the coil 84, a coupler 86 provided on the coil bobbins 84 and 84, and a cylindrical (substantially annular) yoke 87 having magnetism for housing the coil bobbins 84 and 84 and the coils 85 and 85, Consists of. The coil bobbins 84 and 84 and the coils 85 and 85 can be surrounded by the yoke 87.

  The coil bobbin 84 is a resin molded product including a cylindrical portion 84a around which the coil 85 is wound and a pair of flanges 84b and 84c provided at both ends of the cylindrical portion 84a. The pair of coils 85, 85 has a substantially annular shape by being wound around the coil bobbin 84, surrounds the pinion shaft 24 and is arranged side by side in the axial direction of the pinion shaft 24. The coupler 86 is a terminal portion that takes out the detection signals of the pair of coils 85 and 85 to the outside.

The yoke 87 is a magnetic shielding back yoke (coil yoke forming a magnetic path) surrounding the pair of coils 85 and 85, and is made of a magnetic material. The yoke 87 includes a pair of upper and lower yoke bodies 88 and 88 and a single yoke bottom plate 89 that closes the openings 88a and 88a by fitting into the openings 88a and 88a of the yoke bodies 88 and 88, respectively.
The yoke 87 is housed in the housing 51 with its radial movement and axial movement restricted.

  Specifically, the yoke body 88 is a shallow cup-shaped member having a flat bottom 88b, and the flat bottom 88b has a through hole 88c through which the pinion shaft 24 (see FIG. 4) passes on the center line CL1. . The inner diameter of the yoke body 88 is set to be slightly larger than the outer diameters of the flanges 84b and 84c in the coil bobbin 84.

  As shown in FIGS. 6 to 8, the yoke bottom plate 89 is a circular flat plate, has a through hole 89a through which the pinion shaft 24 passes on the center line CL1, and has an outer peripheral surface 89b (that is, a fitting surface 89b). The yoke body 88 has a plurality of press-fitting protrusions 89c that are press-fitted into the inner peripheral surface 88d (that is, the fitting surface 88d of the mating counterpart) in the opening 88a of the yoke body 88. These press-fitting protrusions 89c are small protrusions arranged at an equal pitch with respect to the center line CL1, and for example, the tip has an arc shape.

The yoke bottom plate 89 can be fixed to the yoke body 88 by press-fitting the press-fitting convex portions 89c... Into the mating fitting surface 88d.
When the yoke bottom plate 89 is fitted into the yoke body 88, the press-fitting convex portion 89c is press-fitted only into a part of the mating fitting surface 88d. For this reason, the stress which arises in the yoke 87 by press-fitting can be reduced. By reducing the stress, it is possible to suppress variations in permeability due to deformation of the yoke 87 and residual stress. As a result, variation in output characteristics of the torque sensor 41 (see FIG. 4) can be suppressed.

  As shown in FIGS. 6 and 7, the openings 88a and 88a of the pair of yoke main bodies 88 and 88 each accommodating the coil bobbins 84 and 84 face each other, and one yoke bottom plate 89 is halved in each of the openings 88a and 88a. The coil bobbins 84 and 84 and the coils 85 and 85 can be accommodated in the yokes 87 and 87 by fitting. In this case, the coil bobbins 84 and 84 are sandwiched between the flat bottoms 88 b and 88 b and the yoke bottom plate 89.

  By the way, the yoke 87 has engaging portions 89d and 89d that engage with the plurality of coil bobbins 84 and 84 so as to regulate the positional deviation of the centers of the plurality of coil bobbins 84 and 84 with respect to the center CL1 of the yoke 87. Have.

  More specifically, the coil bobbin 84 has an engaging portion 84d on the surface facing the yoke bottom plate 89 and on the edge of the hole of the cylindrical portion 84a. In other words, the engaging portion 84d is formed at the corner of the flange 84c facing the yoke bottom plate 89 and the cylindrical portion 84a. The engaging portion 84d has a tapered female taper that tapers toward the flat bottom 88b side of the yoke body 88, that is, an axially tapered configuration (configuration in which the corner is chamfered).

  On the other hand, the yoke bottom plate 89 has a pair of engaging portions 89d and 89d that engage with the engaging portions 84d and 84d of the pair of coil bobbins 84 and 84 on both front and back surfaces. The engaging portion 89d of the yoke bottom plate 89 has a tapered shape that matches the engaging portion 84d of the coil bobbin 84, that is, a male taper that is tapered in the axial direction.

  To summarize the above description, as shown in FIGS. 6 and 7, the yoke 87 includes a flat yoke bottom plate 89 (that is, a yoke plate 89) interposed between the pair of coil bobbins 84 and 84. The yoke bottom plate 89 and the pair of coil bobbins 84 and 84 have a tapered engagement with at least one of the yoke bottom plate 89 and the pair of coil bobbins 84 and 84 so as to regulate the positional displacement in the radial direction and / or the axial direction. It has parts 89d and 84d.

  Thus, by fitting the yoke bottom plate 89 into the pair of yoke main bodies 88, 88, the center of the yoke bottom plate 89 can be automatically aligned with the center line CL1 of these yoke main bodies 88, 88.

  Moreover, when the coils 85 and 85 housed in the yoke main bodies 88 and 88 are assembled by being sandwiched between the flat bottom 88b and the yoke bottom plate 89, the female tapered engagement portions 84d and the coil bobbins 84 and 84 are provided. With respect to 84d, the male tapered engaging portions 89d and 89d are automatically engaged individually. These engaging portions 84d and 89d are tapered in the axial direction with the center line CL1 as a reference, and the taper angles are the same or substantially the same. Therefore, by engaging the female and male tapered engaging portions 84d and 89d with each other, the centers of the plurality of coil bobbins 84 and 84 can be automatically matched with the center CL1 of the yoke 87. , Center position shift can be regulated.

Therefore, despite the plurality of coil bobbins 84 and 84, the centers of the coil bobbins 84 and 84 with respect to the center CL1 of the yoke 87 do not shift due to the influence of dimensional tolerance, thermal expansion, vibration, and the like.
Furthermore, it is only necessary to provide one yoke bottom plate 89 to restrict the positional deviation of the pair of yoke bodies 88, 88 with respect to the pair of coil bobbins 84, 84. This reduces the number of parts.

  Thus, the torque sensor 41 (see FIG. 4) can be easily and accurately assembled with a simple configuration. In addition, even if there is a disturbance such as thermal expansion or vibration, there is no bias in the gaps (air gaps) between the pinion shaft 24 and the plurality of coils 85. Therefore, the detection accuracy by the torque sensor 41 can be further increased and a highly accurate state can be maintained.

Furthermore, since the engaging portions 84d and 89d are tapered in the axial direction, in addition to the positional deviation of the center CL1 with respect to the yoke 87, the positional deviation in the axial direction can be restricted. Therefore, the position of the coil bobbin 84 can be accurately aligned with the pinion shaft 24 only by assembling the yoke 87 with respect to the pinion shaft 24 (see FIG. 4).
Moreover, even if there is a disturbance such as thermal expansion or vibration, it is possible to prevent the displacement of the coil 85 in the radial direction and the axial direction with respect to the pinion shaft 24. Therefore, the detection accuracy by the torque sensor 41 can be further increased, and this highly accurate state can be maintained.

  Furthermore, the torque sensor 41 is constituted by a magnetostrictive torque sensor, and as shown in FIG. 1, the steering torque of the steering system 20 applied to the steering handle 21 is detected by this magnetostrictive torque sensor. Steering torque can be detected accurately over a long period of time. By mounting such a high-accuracy magnetostrictive torque sensor in the electric power steering apparatus 10 for a vehicle, it is possible to perform steering torque control with enhanced steering feeling (steering feeling) based on more accurate steering torque. it can.

  As shown in FIG. 4, a leaf spring 91 is interposed between the lower end of the bearing holding member 62 and the yoke body 88 in the detection unit 83 below the bearing holding member 62. The leaf spring 91 is a member for removing the backlash by absorbing the axial clearance between the bearing holding member 62 and the detection portions 83 and 83 housed in the housing 51. It consists of an annular spring, for example a disc spring.

Next, a second embodiment of the detection unit 83 will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected about the structure similar to the said 1st Example, and the description is abbreviate | omitted.
FIG. 9 is a cross-sectional view of the detecting portion (second embodiment) of the torque sensor according to the present invention. FIG. 10 is an enlarged view of the detection unit (second embodiment) shown in FIG.

As shown in FIGS. 9 and 10, the detection unit 83 of the second embodiment is characterized in that the engagement portions 84d and 89d of the first embodiment are changed.
More specifically, the coil bobbin 84 is housed in the yoke 87 in the direction opposite to that of the first embodiment, and has an engaging portion 84d at the edge of the outer peripheral portion of the flange 84b facing the yoke bottom plate 89. The engaging portion 84d in this case is a male taper that tapers in the axial direction toward the yoke bottom plate 89 side. On the other hand, the engaging portion 89d of the yoke bottom plate 89 is a tapered shape that matches the engaging portion 84d of the coil bobbin 84, that is, a female taper that is tapered in the axial direction.
This second embodiment also exhibits the same operations and effects as the first embodiment.

Next, a third embodiment of the detection unit 83 will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected about the structure similar to the said 1st-2nd Example, The description is abbreviate | omitted.
FIG. 11 is an enlarged view around a torque sensor (third embodiment) according to the present invention. FIG. 12 is a cross-sectional view of the detecting portion (third embodiment) of the torque sensor according to the present invention. FIG. 13 is an enlarged view of the detection unit (third embodiment) shown in FIG.

As shown in FIGS. 11 to 13, the detection unit 83 of the third embodiment is characterized in that a coil bobbin 84, a coil 85, and a yoke body 88 are provided one by one.
To summarize the above description, as shown in FIGS. 12 and 13, the yoke 87 (that is, the flat yoke bottom plate 89 and the yoke plate 89) and the coil bobbin 84 are positioned in the radial direction and / or the axial direction. At least one of the yoke 87 and the coil bobbin 84 is provided with tapered engagement portions 89d and 84d so as to restrict the displacement.

  This third embodiment also exhibits the same operations and effects as the first and second embodiments. That is, by engaging the female and male tapered engaging portions 84d and 89d, the center of the coil bobbin 84 can be automatically matched with the center CL1 of the yoke 87, and the center position is shifted. Can be regulated. In addition to the position shift of the center CL1 with respect to the yoke 87, the position shift in the axial direction can also be restricted.

Next, a fourth embodiment of the detection unit 83 will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected about the structure similar to the said 1st-3rd Example, The description is abbreviate | omitted.
FIG. 14 is a cross-sectional view of the detecting portion (fourth embodiment) of the torque sensor according to the present invention. FIG. 15 is an enlarged view of the detection unit (fourth embodiment) shown in FIG.

As shown in FIGS. 14 and 15, the detection unit 83 of the fourth embodiment is a modification of the second embodiment. It is characterized by being made into pieces. Further, the fourth embodiment is characterized in that the flange 84b of the coil bobbin 84 has a male tapered engaging portion 84d, and the yoke bottom plate 89 has a female tapered engaging portion 89d.
Also in the fourth embodiment, the same operations and effects as the first to third embodiments are exhibited.

  In the embodiment of the present invention, the press-fitting convex portion 89c is provided so as to press-fit the mating fitting surface of at least one of the yoke body 88 and the yoke bottom plate 89 (yoke plate 89). Any configuration may be used.

  The torque sensor 41 of the present invention is suitable for the vehicular electric power steering apparatus 10 that detects the steering torque generated by the steering handle 21 and transmits the detection signal to the electric motor 43 to generate auxiliary torque. .

1 is a schematic diagram of an electric power steering apparatus according to the present invention. 1 is an overall configuration diagram of an electric power steering apparatus according to the present invention. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is an enlarged view around a torque sensor shown in FIG. 3. FIG. 5 is a cross-sectional view and action diagram of the free end bearing and the elastic body shown in FIG. 4. It is sectional drawing of the detection part (1st Example) of the torque sensor which concerns on this invention. It is the enlarged view which decomposed | disassembled the detection part (1st Example) shown in FIG. FIG. 8 is a view on arrow 8-8 in FIG. 7. It is sectional drawing of the detection part (2nd Example) of the torque sensor which concerns on this invention. It is the enlarged view which decomposed | disassembled the detection part (2nd Example) shown in FIG. It is an enlarged view around a torque sensor (third embodiment) according to the present invention. It is sectional drawing of the detection part (3rd Example) of the torque sensor which concerns on this invention. It is the enlarged view which decomposed | disassembled the detection part (3rd Example) shown in FIG. It is sectional drawing of the detection part (4th Example) of the torque sensor which concerns on this invention. It is the enlarged view which decomposed | disassembled the detection part (4th Example) shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 20 ... Steering system, 21 ... Steering handle, 24 ... Rotating shaft (pinion shaft), 29 ... Steering wheel, 41 ... Torque sensor, 43 ... Electric motor, 44 ... Worm gear mechanism, 81, 82 ... Magnetostrictive film, 84 ... Coil bobbin, 84d ... Coil bobbin engaging part, 85 ... Coil, 87 ... Yoke, 88 ... Yoke main body, 88a ... Opening of yoke main body, 88d ... Opposite fitting surface, 89 ... Yoke bottom plate, 89b ... One Fitting surface, 89c ... press-fitting convex part, 89d ... engaging part of yoke, CL1 ... center of yoke.

Claims (4)

A torque sensor for detecting a torque acting on the rotating shaft by a coil arranged so as to surround the rotating shaft, a coil bobbin that winds the coil, and a magnetic yoke that houses the coil and the coil bobbin. In the provided torque sensor,
The yoke and the coil bobbin have a tapered engaging portion on at least one of the yoke and the coil bobbin so as to regulate the displacement in the radial direction and / or the axial direction of each other. Torque sensor. A torque sensor for detecting torque acting on the rotating shaft by a pair of coils surrounding the rotating shaft and arranged in the axial direction of the rotating shaft, and a pair of coil bobbins each winding the pair of coils; In a torque sensor comprising a pair of coils and a magnetic yoke that houses a pair of coil bobbins,
The yoke includes a flat yoke plate interposed between the pair of coil bobbins,
The yoke plate and the pair of coil bobbins have a taper-shaped engaging portion on at least one of the yoke plate and the pair of coil bobbins so as to regulate the positional displacement in the radial direction and / or the axial direction. Torque sensor characterized by A torque sensor for detecting a torque acting on the rotating shaft by a coil arranged so as to surround the rotating shaft, a coil bobbin that winds the coil, and a magnetic yoke that houses the coil and the coil bobbin. In the provided torque sensor,
The yoke or the coil bobbin has an engaging portion on at least one of the yoke and the coil bobbin so as to regulate the displacement in the radial direction and / or the axial direction of each other,
The yoke consists of a cup-shaped yoke body and a yoke bottom plate that closes the opening by fitting into the opening of the yoke body.
The torque sensor according to claim 1, wherein at least one fitting surface of the yoke main body and the yoke bottom plate has a press-fitting convex portion for press-fitting the mating fitting surface.   The torque sensor according to claim 1, 2, or 3 is a sensor that detects a steering torque of a steering system applied to a steering handle for a vehicle, and is provided on a surface of the rotating shaft to adjust the torque. A torque sensor comprising a magnetostrictive torque sensor having a magnetostrictive film whose magnetostrictive characteristics change in response to the magnetostrictive effect generated in the magnetostrictive film by the coil.

Images