Title of the invention: Torque detection device and its assembly method, electric power steering device
Technical field
[0001]
　The present invention relates to a torque detection device for detecting an input torque, an assembly method thereof, and an electric power steering device including the torque detection device.
Background technology
[0002]
　FIG. 14 shows an example of a conventionally known electric power steering device. The steering wheel 1 is fixed to the rear end portion of the steering shaft 2, and the steering shaft 2 is rotatably supported inside a cylindrical steering column 3 supported by a vehicle body. When the driver rotates the steering wheel 1, this rotation is transmitted to the pinion shaft 7 constituting the rack and pinion type steering gear unit 6 via the steering shaft 2, the universal joint 4a, the intermediate shaft 5, and the universal joint 4b. Be transmitted. When the pinion shaft 7 rotates, a pair of tie rods 9 and 9 connected to both ends of the rack shaft 8 constituting the steering gear unit 6 are pushed and pulled, and the amount of operation of the steering wheel 4 is applied to the pair of left and right steering wheels. The steering angle is given according to.
[0003]
　Further, in the illustrated electric power steering device, the housing 10 is fixed to the front end portion of the steering column 3. The housing 10 supports the electric motor 11 and houses a torque detection device and a speed reducer (not shown). When torque is applied to the steering shaft 2 based on the operation of the steering wheel 1, the torque detecting device detects the direction and magnitude of the torque. Then, the energization of the electric motor 11 is controlled by using the direction and magnitude of this torque. As a result, the electric motor 11 generates auxiliary power according to the direction and magnitude of the torque. This auxiliary power is applied to a portion of the housing 10 that rotates with the steering shaft 2 after being increased by the speed reducer. As a result, the force required for the driver to operate the steering wheel 1 is reduced.
[0004]
　Patent Document 1 describes a specific structure of a torque detection device incorporated in an electric power steering device. In this structure, the steering shaft, which is a torque transmission shaft, and the output shaft to which auxiliary power is applied are coaxially connected by a torsion bar. Further, a torque detection uneven portion is provided on the outer peripheral surface of the output shaft, and a torque detection sleeve coaxially arranged on the radial outer side of the torque detection uneven portion is coupled to the end portion of the steering shaft. Further, a coil coaxially arranged on the radial outer side of the torque detection sleeve is supported by the housing. In an electric power steering device equipped with such a torque detection device, when torque is applied to the steering shaft by operating the steering wheel, the torsion bar is elastic by the amount corresponding to the direction and magnitude of the torque. Twist in. Along with this, the positional relationship between the torque detection uneven portion and the torque detection sleeve in the circumferential direction changes, so that the impedance of the coil changes. Therefore, the direction and magnitude of the torque can be detected based on this impedance change.
Prior art literature
Patent documents
[0005]
Patent Document 1: International Publication No. 2014/199959
Outline of the invention
Problems to be solved by the invention
[0006]
　In the conventional structure described in Patent Document 1, the end of the torque detection sleeve is fitted on the end of the steering shaft, and one circumferential groove is provided on the outer peripheral surface of the end of the steering shaft. The torque detection sleeve is coupled to the steering shaft by engaging the caulking portion formed on the edge portion of the torque detection sleeve. That is, in the conventional structure, only one set of engaging portions between the circumferential groove and the caulking portion, which contributes to the coupling force of the torque detection sleeve with respect to the steering shaft, is provided. Therefore, there is room for improvement in terms of enhancing the coupling force and safety of the joint portion between the steering shaft (torque transmission shaft) and the torque detection sleeve.
[0007]
　An object of the present invention is to realize a structure capable of enhancing the coupling force and safety of a joint portion between a torque transmission shaft and a torque detection sleeve.
Means to solve problems
[0008]
　The torque detection device of the present invention includes a torque transmission shaft and a cylindrical torque detection sleeve having a plurality of window holes on one side in the axial direction.
　The torque transmission shaft has circumferential grooves formed in the circumferential direction at a plurality of axial directions on the outer peripheral surface and are parallel to each other.
　The torque detection sleeve is fitted onto the torque transmission shaft so that the other side portion in the axial direction covers the entire circumference (entire circumference and width) of the circumferential groove, and each of the circumferential grooves. A crimped portion crimped to the circumferential groove is provided in an axial portion that overlaps with the radial direction.
[0009]
　In the torque detection device of the present invention, each of the circumferential grooves can have the same shape as each other.
[0010]
　In the torque detection device of the present invention, at least one of the circumferential grooves can have a shape different from that of the other circumferential grooves.
[0011]
　In the torque detection device of the present invention, the circumferential groove includes an outer opening groove in which a pair of inner side surfaces located on both sides in the axial direction are inclined in a direction away from each other with respect to the axial direction toward the outer side in the radial direction. It can be assumed that the caulking portion is in contact with each of the inner side surfaces of the pair of the outer opening grooves.
[0012]
　In the torque detection device of the present invention, the inclination angle of the pair of inner surfaces with respect to the central axis of the circumferential groove can be set to 50 degrees to 70 degrees.
[0013]
　In the torque detection device of the present invention, the torque transmission shaft is provided with a plurality of axial grooves in a plurality of locations in the circumferential direction of the outer peripheral surface, and the
　torque detection sleeve is provided with the axial groove on the other side in the axial direction. Positioning convex portions projecting inward in the radial direction may be provided at a plurality of locations having the same phase, and the positioning convex portions may
　be provided on one side in the axial direction with respect to the caulking portion.
[0014]
　The method of assembling the torque detection device of the present invention includes
　a step of externally fitting the other side portion of the torque detection sleeve in the axial direction to the torque transmission shaft so as to cover the entire circumferential groove, and the
　torque detection sleeve. Of these, for each of the circumferential groove and the axial portion overlapping in the radial direction, a plurality of claws arranged in the circumferential direction are arranged on the radial outer side of the axial portion, and the axial portion is formed. The step of forming the crimped portion in the axial portion by pressing the plurality of claws from the outer side in the radial direction to the inner side in the radial direction is included.
[0015]
　In the method of assembling the torque detection device of the present invention, in the step of forming the caulking portion, the work of forming the caulking portion with respect to each of the axial portions is close to one side portion in the axial direction of the torque detection sleeve. It can be done in order from the axial part.
[0016]
　In the method of assembling the torque detection device of the present invention, in the step of forming the caulking portion, the number of the claws for forming the caulking portion can be made equal for each of the axial portions.
　In this case, the phases of the arrangement of the claws for forming the crimped portion in the circumferential direction can be matched for each of the axial portions.
　Alternatively, the phase of the arrangement of the claws in the circumferential direction for forming the crimped portion can be made different for each of the axial portions.
[0017]
　In the method of assembling the torque detection device of the present invention, in the step of forming the caulking portion, the number of the claws for forming the caulking portion can be made different for each of the axial portions.
[0018]
　The electric power steering device of the present invention includes the torque detection device of the present invention.
Effect of the invention
[0019]
　According to the present invention, it is possible to enhance the coupling force and safety of the joint portion between the torque transmission shaft and the torque detection sleeve.
A brief description of the drawing
[0020]
FIG. 1 is a partially cut side view of the electric power steering device according to the first embodiment.
FIG. 2 is an enlarged view of part A of FIG.
FIG. 3 is an exploded perspective view of an element for detecting torque according to the first embodiment.
FIG. 4 is an enlarged view of the right side portion of FIG.
FIG. 5 is a view of the torque detection sleeve and its peripheral portion as viewed from the outside in the radial direction according to the first embodiment.
FIG. 6 is a perspective view of a torque detection sleeve, a front end of a lower shaft, and a portion of a torsion bar according to the first embodiment.
FIG. 7 is an enlarged view of part B of FIG.
FIG. 8 is an enlarged view of part C of FIG. 7, showing only the lower shaft taken out.
9 (a) to 9 (c) are cross-sectional views showing, in order of steps, the work of connecting the torque detection sleeve to the front end portion of the steering shaft with respect to the first embodiment.
10 (a) and 10 (b) show that, with respect to the first embodiment, the axial rear end portion of the torque detection sleeve is crimped to the circumferential groove formed on the outer peripheral surface of the front end portion of the lower shaft. It is a figure seen from the axial direction which shows the work to attach in the order of a process.
FIG. 11 is a diagram corresponding to FIG. 8 with respect to the second embodiment.
FIG. 12 (a) is a view corresponding to FIG. 10 (b) when the axial rear end portion of the torque detection sleeve is crimped to the circumferential groove on the front side in the axial direction, and is FIG. 12 (b). Is a diagram corresponding to FIG. 10B when the rear end portion in the axial direction of the torque detection sleeve is crimped to the circumferential groove on the rear side in the axial direction.
FIG. 13 is an enlarged cross-sectional view showing a state in which the axial rear end portion of the torque detection sleeve is crimped to the circumferential groove on the front side in the axial direction.
FIG. 14 is a partially cut side view showing an example of a conventionally known electric power steering device.
Mode for carrying out the invention
[0021]
[First Embodiment]
　The first embodiment will be described with reference to FIGS. 1 to 10.
　The electric power steering device of the present embodiment includes a steering column 3a, a steering shaft 2a, a housing 10a, an output shaft 12, a torsion bar 13, a torque detection sleeve 14, a torque detection coil unit 15, and a substrate 16. , A worm reducer 17, and an electric motor 11a.
　Further, the electric power steering device of the present embodiment includes a torque detection device, and the torque detection device includes a lower shaft 21 constituting the steering shaft 2a, an output shaft 12, a torsion bar 13, and torque detection. The sleeve 14 and the torque detection coil unit 15 are included.
　Regarding the electric power steering device, the front-rear direction refers to the front-rear direction of the vehicle unless otherwise specified. For example, in FIGS. 1 to 9, the left side is the front and the right side is the back.
[0022]
　The steering column 3a includes a cylindrical inner column 18 arranged on the front side and an outer column 19 arranged on the rear side. The inner column 18 and the outer column 19 are stretchably combined and supported by the vehicle body by the support bracket 20. The inner column 18 and the outer column 19 are made of steel or a light alloy such as an aluminum alloy.
[0023]
　The steering shaft 2a includes a lower shaft 21 arranged on the front side and a hollow shaft-shaped upper shaft 22 arranged on the rear side. The lower shaft 21 and the upper shaft 22 are spline-fitted so as to enable torque transmission and relative displacement in the axial direction, and are rotatably supported inside the steering column 3a. The lower shaft 21 and the upper shaft 22 are made of steel. The steering wheel 1 (see FIG. 13) is fixed to the rear end portion of the upper shaft 22 protruding from the rear end opening of the outer column 19.
[0024]
　The housing 10a is formed by connecting the front lid 23 and the rear main body 24 to each other by a plurality of bolts (not shown), and is coupled and fixed to the front end of the inner column 18. The lid 23 and the main body 24 are made of a light alloy such as an aluminum alloy or a synthetic resin. The front end portion of the lower shaft 21 is inserted inside the housing 10a.
[0025]
　The output shaft 12 is made of steel, which is a magnetic metal, into a hollow shaft shape. The output shaft 12 is rotatably supported by a pair of ball bearings 25 and 26 on the front side of the lower shaft 21 in the housing 10a. A universal joint 4a (see FIG. 13) is coupled to the front end portion of the output shaft 12 protruding from the front end opening of the housing 10a.
[0026]
　The torsion bar 13 is made of spring steel in a stepped columnar shape. The lower shaft 21 and the output shaft 12 are coaxially connected to each other by a torsion bar 13. That is, most of the torsion bar 13 except the rear end is arranged inside the output shaft 12. Further, the front end portion of the torsion bar 13 is connected to the front end portion of the output shaft 12 by a pin 27 so as not to rotate relative to each other, and the rear end portion is provided at the radial center portion of the front side portion of the lower shaft 21. The spline hole 28 is fitted with a spline so as not to rotate relative to the spline hole 28.
[0027]
　The lower shaft 21, which is a torque transmission shaft, has a cylindrical tubular portion 29 at the front end portion. The tubular portion 29 has a female stopper portion 30 having an uneven shape (gear shape) in the circumferential direction on the inner peripheral surface. The female stopper portion 30 is formed by arranging a plurality of tooth portions 31, each of which is long in the axial direction, at equal intervals in the circumferential direction.
[0028]
　The output shaft 12 has a male stopper portion 32 having an uneven shape (gear shape) in the circumferential direction on the outer peripheral surface of the rear end portion. The male stopper portion 32 is formed by arranging a plurality of groove portions 33 (the same number as the tooth portions 31), each of which is long in the axial direction, at equal intervals in the circumferential direction.
[0029]
　The female stopper portion 30 and the male stopper portion 32 are concave-convexly engaged with each other so as to enable relative rotation within a predetermined angle range (for example, within a range of ± 5 degrees based on a neutral state in which the torsion bar 13 is not twisted). That is, the tooth portion 31 constituting the female stopper portion 30 is loosely engaged with the groove portion 33 constituting the male stopper portion 32 with a gap in the circumferential direction interposed therebetween, so that the lower shaft 21 and the output shaft 12 are relative to each other. Rotation is regulated within a predetermined angle range. This prevents the torsion bar 13 from being excessively twisted.
[0030]
　The output shaft 12 has a torque detection uneven portion 34 having a concave-convex shape in the circumferential direction at a portion adjacent to the front side in the axial direction with respect to the male stopper portion 32 on the outer peripheral surface of the rear side portion. The torque detection uneven portion 34 is formed by arranging a plurality of groove portions 35, each of which is long in the axial direction, at equal intervals in the circumferential direction. The torque detection uneven portion 34 has an outer diameter dimension (diameter of the circumscribed circle) larger than that of the male stopper portion 32. In the illustrated example, the same number of groove portions 35 forming the torque detection uneven portion 34 and the same number of groove portions 33 forming the male stopper portion 32 are provided, and the phases of arrangement in the circumferential direction are in agreement with each other.
[0031]
　The torque detection sleeve 14 is made of a conductive non-magnetic metal such as an aluminum alloy in a cylindrical shape. In the torque detection sleeve 14, the axial front side portion, which is one side portion in the axial direction, is coaxially arranged on the radial outer side of the torque detection uneven portion 34, and the axial rear end portion, which is the other side portion in the axial direction, is tubular. It is supported by the portion 29 in a cantilevered state.
[0032]
　The axially front side portion of the torque detection sleeve 14 arranged coaxially on the radial outer side of the torque detection uneven portion 34 has a first window hole row and a second window hole row separated in the axial direction. The first window hole row located on the front side in the axial direction is formed by arranging a plurality of rectangular window holes (through holes) 36a (the same number as the groove portions 35) at equal intervals in the circumferential direction. The second window hole row located on the rear side in the axial direction is formed by arranging a plurality of rectangular window holes (through holes) 36b (the same number as the grooves 35) at equal intervals in the circumferential direction. The phases of the arrangements of the window holes 36a of the first window hole row and the window holes 36b of the second window hole row in the circumferential direction are shifted by half a pitch from each other.
[0033]
　The tubular portion 29 has a plurality of axial grooves 37 and a pair of circumferential grooves 38 on the outer peripheral surface. The plurality of axial grooves 37 are arranged at a plurality of locations (4 locations in the illustrated example) at equal intervals in the circumferential direction of the outer peripheral surface of the tubular portion 29, and each of them covers the entire length of the outer peripheral surface of the tubular portion 29. It is provided. The pair of circumferential grooves 38 are arranged in parallel at two locations separated in the axial direction on the outer peripheral surface of the tubular portion 29, and the tubular portion 29 intersects the plurality of axial grooves 37, respectively. It is provided over the entire circumference of the outer peripheral surface of the. In this embodiment, the pair of circumferential grooves 38 have the same shape as each other. Each of the pair of circumferential grooves 38 is an outward opening groove. That is, as shown in FIGS. 7 and 8, each of the pair of circumferential grooves 38 is separated from each other in the axial direction so that each of the pair of inner side surfaces 46 located on both sides in the axial direction is oriented outward in the radial direction. It has a partial conical surface shape that is inclined in the direction. Each bottom surface 45 of the pair of circumferential grooves 38 has a cylindrical surface shape. In the present embodiment, when a pair of circumferential grooves 38 is machined on the outer peripheral surface of the tubular portion 29, each of the pair of circumferential grooves 38 is cut by one chucking. Therefore, the inclinations of the pair of circumferential grooves 38 are the same, and as a result, the caulking portion 40, which will be described later, is stably formed for each of the pair of circumferential grooves 38.
[0034]
　The axial rear end portion of the torque detection sleeve 14 is fitted onto the tubular portion 29 so as to cover the entire pair of circumferential grooves 38 by the axial intermediate portion thereof. Further, the axial rear end portion of the torque detection sleeve 14 is crimped to the circumferential groove 38 over the entire circumference in the axial portion overlapping each of the pair of circumferential grooves 38 in the radial direction. It has a pair of caulking portions 40. That is, each of the pair of caulking portions 40 is engaged with the circumferential groove 38 without any axial rattling. More specifically, each of the pair of caulking portions 40 is in contact with at least one pair of inner side surfaces 46 of the bottom surface 45 and the pair of inner side surfaces 46 constituting the circumferential groove 38. As a result, the torque detection sleeve 14 is positioned in the axial direction with respect to the tubular portion 29, and relative displacement in the axial direction is prevented. Further, the tubular portion 29 and the torque detection sleeve 14 are formed by the tension and frictional forces acting on the contact portions between each of the pair of caulking portions 40 and at least one pair of inner side surfaces 46 of the circumferential groove 38. Relative rotation is prevented.
[0035]
　At the rear end of the torque detection sleeve 14 in the axial direction, positioning protrusions protruding inward in the radial direction at a plurality of locations on the front side in the axial direction of the pair of caulking portions 40 and having the same phase as the axial groove 37 in the circumferential direction. 39 is provided. Then, each of the positioning convex portions 39 is engaged with the axial groove 37 without rattling in the circumferential direction. As a result, the torque detection sleeve 14 is positioned in the rotational direction with respect to the tubular portion 29, and relative rotation is prevented.
[0036]
　In this way, by providing the positioning convex portion 39 on the front side in the axial direction with respect to the caulking portion 40, the distance into which the axial groove 37 is inserted with respect to the positioning convex portion 39 can be shortened, whereby the positioning convex portion 39 can be shortened. It is possible to prevent the inner peripheral surface of 39 from being scraped. On the other hand, the positioning of the positioning convex portion 39 and the axial groove 37 in the rotational direction is performed with the lower shaft 21 inserted to some extent with respect to the torque detection sleeve 14, so that the lower shaft 21 and the torque detection sleeve 14 It is hard to bend and easy to assemble.
[0037]
　Each of the positioning convex portions 39 is formed before the axial rear end portion of the torque detection sleeve 14 is fitted onto the tubular portion 29. In the present embodiment, since each of the positioning convex portions 39 is formed by embossing, concave portions are formed on the back surface side (outer diameter side) of each of the positioning convex portions 39. On the other hand, each of the pair of caulking portions 40 is formed after the axial rear end portion of the torque detection sleeve 14 is fitted onto the tubular portion 29. 3 and 4 show the torque detection sleeve 14 in a state before the pair of caulking portions 40 is formed.
[0038]
　When assembling the electric power steering device of the present embodiment, the work of externally fitting and supporting the axial rear end portion of the torque detection sleeve 14 to the tubular portion 29 is performed as follows.
　First, in a state where the positioning convex portion 39 of the torque detection sleeve 14 and the axial groove 37 (see FIGS. 3 to 6) of the tubular portion 29 are in phase with each other in the circumferential direction, FIGS. 9 (a) → 9 (FIG. 9). As shown in b), the axial rear end portion of the torque detection sleeve 14 is fitted onto the outer peripheral surface of the tubular portion 29 without any radial rattling from the axial front side. As a result, of the axial rear end portion of the torque detection sleeve 14, the axial intermediate portion, which is a portion located on the front side of the axial rear end edge portion, covers the entire pair of circumferential grooves 38. .. Further, with such an outer fitting operation, each of the positioning convex portions 39 is engaged with the axial groove 37 without rattling in the circumferential direction. The positional relationship between the torque detection sleeve 14 and the tubular portion 29 in the axial direction in the state shown in FIG. 9B is the window hole 36a and the window hole 36b in the state where the electric power steering device is assembled. The positional relationship between the torque detection coil unit and the torque detection coil unit 15 in the axial direction is determined to be a predetermined positional relationship, and specifically, the position is determined based on the axial position of the axial front end edge of the torque detection sleeve 14. Therefore, the axial position of the axial rear end edge of the torque detection sleeve 14 with respect to the tubular portion 29 in the state shown in FIG. 9B varies in the axial direction due to the variation in the member dimensions. However, in the present embodiment, even if such an axial variation occurs, the entire pair of circumferential grooves 38 can always be covered by the axial rear end portion of the torque detection sleeve 14. In other words, the torque detection sleeve 14 has a margin in the axial dimension so that the axial rear end edge of the torque detection sleeve 14 is located on the axial rear side of the circumferential groove 38 on the axial rear side. I'm letting you.
　Next, as shown in FIG. 9B → FIG. 9C, of ​​the axial rear end portion of the torque detection sleeve 14, the axial portion overlapping each of the pair of circumferential grooves 38 in the radial direction. Is plastically deformed (caulked) from the outer side in the radial direction to the inner side in the radial direction over the entire circumference. As a result, the crimped portion 40 is formed in each of the axial portions, and at the same time, the crimped portion 40 is engaged with each of the circumferential grooves 38.
[0039]
　Therefore, in the present embodiment, with respect to each of the pair of circumferential grooves 38 and the axial portion overlapping in the radial direction of the torque detection sleeve 14, FIG. As shown in a), a plurality of (six in this embodiment) claws 41 arranged in the circumferential direction are arranged. Then, as shown in FIG. 10A → FIG. 10B, these plurality of claws 41 are moved in the radial direction in synchronization with each other. As a result, the axial portion of the torque detection sleeve 14 is strongly pressed from the radial outer side to the radial inner side by the radial inner ends of the plurality of claws 41. As a result, the crimped portion 40 is formed by plastically deforming the axial portion from the outer side in the radial direction to the inner side in the radial direction over the entire circumference.
[0040]
　Further, when the axial portion of the torque detection sleeve 14 is deformed according to the shape of the circumferential groove 38 by the squeezing caulking by the claw 41 and then the claw 41 is retracted from the caulking portion 40, the caulking portion 40 springs back. Then, it is stretched between the pair of inner side surfaces 46 of the circumferential groove 38, and a frictional force is generated between the caulking portion 40 and the pair of inner side surfaces 46. Here, by setting the inclination angle θ of the inner side surface 46 with respect to the central axis of the circumferential groove 38 shown in FIG. 8 to 50 to 70 degrees (preferably 60 degrees), this springback causes the caulking portion 40 to be formed. The surface pressure between the pair of inner side surfaces 46 increases, and the holding force of the torque detection sleeve 14 by the caulking portion 40 can be increased.
[0041]
　Further, in the present embodiment, the work of forming the caulking portion 40 for each of the pair of circumferential grooves 38 and the axial portion overlapping in the radial direction of the torque detection sleeve 14 is performed on the shaft of the torque detection sleeve 14. Direction Perform in order from the axial part closest to the front side part. That is, first, the caulking portion 40 is formed in the axial portion located on the front side in the axial direction, and then the caulking portion 40 is formed in the axial portion located on the rear side in the axial direction. As a result, the torque detection sleeve 14 and the tubular portion 29 can be reliably connected in a predetermined positional relationship.
[0042]
　When carrying out the present invention, the number of claws 41 forming one caulking portion 40 is arbitrary of two or more as long as the coaxiality between the tubular portion 29 and the torque detection sleeve 14 can be secured. Can be the number of. As the number of claws 41 is increased, the influence of a defect such as wear on one claw 41, that is, the adverse effect on the accuracy of the caulking portion 40 can be suppressed to a small extent. In the present embodiment, since the number of claws 41 is 6, the influence can be suppressed to 1/6 (about 17%). Further, when the present invention is carried out, the phase of the arrangement of the plurality of claws 41 prepared for each axial portion to form the caulking portion 40 in the circumferential direction is such that the plurality of claws 41 for each axial portion are arranged. They may be matched with each other or different from each other, but in the present embodiment, they are matched with each other.
[0043]
　The torque detection coil unit 15 is formed in a cylindrical shape, and is coaxially arranged on the radial outer side of the torque detection uneven portion 34 and the torque detection sleeve 14. The torque detection coil unit 15 is internally fitted and fixed to the housing 10a, and includes a pair of coils 42a and 42b separated in the axial direction. The coil 42a located on the front side in the axial direction is arranged so as to overlap the window hole 36a of the first window hole row in the radial direction, and the coil 42b located on the rear side in the axial direction is the window hole of the second window hole row. It is arranged so as to overlap with 36a in the radial direction.
[0044]
　The substrate 16 is installed in the housing 10a at one location in the circumferential direction (below the torque detection coil unit 15 in the illustrated example) on the outer side in the radial direction of the torque detection coil unit 15. A motor control circuit is configured on the substrate 16. The ends of the coils 42a and 42b are connected to this motor control circuit.
[0045]
　The worm reducer 17 is arranged in the housing 10a and includes a worm wheel 43 and a worm 44. The worm wheel 43 is externally fitted and fixed to the axially intermediate portion of the output shaft 12 between the ball bearings 25 and 26. The worm 44 is rotatably supported in the housing 10a in a state of being meshed with the worm wheel 43.
[0046]
　The electric motor 11a is supported by the housing 10a. The output shaft of the electric motor 11a is coupled to the base end portion of the worm 44 so as to be able to transmit torque.
[0047]
　In the electric power steering device of the present embodiment, when the driver operates the steering wheel 1 to apply torque, which is a steering force, to the steering shaft 2a, only the amount corresponding to the direction and magnitude of the torque is applied. , The torsion bar 13 is elastically twisted (within a predetermined angle range). Along with this, the positional relationship between the torque detection uneven portion 34 and the torque detection sleeve 14 in the circumferential direction changes, so that the impedance of the coils 42a and 42b constituting the torque detection coil unit 15 changes. Therefore, the direction and magnitude of the torque can be detected based on this impedance change. The motor control circuit on the substrate 16 detects the direction and magnitude of the torque in this way, and uses the detection result of the torque to control the energization of the electric motor 11a, whereby the electric motor 11a , Generates auxiliary power according to the direction and magnitude of torque. This auxiliary power is applied to the output shaft 12 after being increased by the worm reducer 17. As a result, the force required for the driver to operate the steering wheel 1 is reduced.
[0048]
　In the electric power steering device of the present embodiment as described above, the circumferential groove 38 provided on the outer peripheral surface of the tubular portion 29 of the lower shaft 21 and the axial rear end portion of the torque detection sleeve 14 are formed. Two sets of engaging portions with the caulking portion 40 are provided so as to be separated from each other in the axial direction. Therefore, as compared with the case where only one set of the engaging portions is provided as in the conventional structure, the coupling force between the tubular portion 29 and the torque detection sleeve 14 (relative displacement in the axial direction and the rotational direction is prevented). It is possible to increase the robustness (stability) of this binding force. Therefore, it is possible to prevent the tubular portion 29 and the torque detection sleeve 14 from being relatively displaced in the axial direction and the rotational direction due to the vibration of the vehicle or the inertia due to the eccentricity of the torque detection sleeve 14 for a long period of time, and the reliability is high. Torque detection can be performed. Further, in the present embodiment, since the two sets of the engaging portions are provided, even if the engagement of one engaging portion is impaired, the engagement of the other engaging portion causes the tubular portion 29. It is possible to ensure double safety, such as being able to maintain the coupled state between the force and the torque detection sleeve 14.
[0049]
　Further, in the present embodiment, a plurality of claws 41 arranged in the circumferential direction are arranged on the radial outside of each of the pair of circumferential grooves 38 and the axial portion overlapping in the radial direction of the torque detection sleeve 14. Then, by pressing each of the axial portions from the radially outer side to the radial inner side by a plurality of claws 41 arranged for each of the axial portions, a caulking portion 40 is formed in each of the axial portions. I try to do it. When the caulking portion 40 is formed in this way, a force that causes an axial deviation between the torque detection sleeve 14 and the tubular portion 29 does not substantially act. Therefore, it is possible to easily prevent the torque detection sleeve 14 and the tubular portion 29 from shifting in the axial direction when the caulking portion 40 is formed.
[0050]
　In the structure of the present embodiment, for example, the following specifications can be adopted for the torque detection sleeve 14 and the tubular portion 29 (see FIGS. 8 and 9).
　　Thickness dimension t of torque detection sleeve 14: 0.20 mm to 1.0 mm
　　Outer diameter dimension D of tubular portion 29: 20 mm to 30 mm (for example, 23.5 mm)
　　Axial width dimension x of opening of circumferential groove 38 1.0 mm ~ 2.0 mm (e.g. 1.5 mm)
　　depth of the circumferential groove 38 y: 0.4 mm or more (more than 1.7% of the outer diameter D)
　　inner surface 46 with respect to the central axis of the circumferential grooves 38 Tilt angle θ: 50 degrees to 70 degrees (for example, 60 degrees)
　　Axial distance between a pair of circumferential grooves 38 L: 0.3 mm to 5 mm (for example, 0.7 mm) When
　the tilt angle θ is set to 60 degrees It is easy to maintain the coupling force of the torque detection sleeve 14 with respect to the tubular portion 29 even when a force larger than the inertial force such as vibration when traveling on a rough road is applied as well as the inertial force at the time of steering.
　The smaller the value of the axial spacing L, the more space can be saved.
[0051]
[Second Embodiment]
　The second embodiment will be described with reference to FIGS. 11 to 13.
　In the present embodiment, the pair of circumferential grooves 38a and 38b formed parallel to the outer peripheral surface of the tubular portion 29a of the lower shaft 21a have different shapes. Specifically, the pair of circumferential grooves 38a and 38b have different depth dimensions y1 and y2 (y1> y2 in the illustrated example). Further, the pair of circumferential grooves 38a and 38b have different inclination angles θ1 and θ2 on the inner side surfaces 46a and 46b of each other (in the illustrated example, θ1> θ2). As described above, in the present embodiment, the coupling force of the torque detection sleeve 14a with respect to the tubular portion 29a is adjusted by causing the pair of circumferential grooves 38a and 38b to have different shapes from each other. Further, in the present embodiment, the axial distance L1 between the pair of circumferential grooves 38a and 38b is made larger than that in the case of the first embodiment (L1> L).
[0052]
　Further, in the present embodiment, the number of claws 41a for forming the caulking portion 40a to be engaged with the circumferential groove 38a on the front side in the axial direction and the caulking portion 40b to be engaged with the circumferential groove 38b on the rear side in the axial direction are provided. The number of claws 41b to be formed is four, which is a smaller number than in the case of the first embodiment. That is, in the present embodiment, the number of the claws 41a and 41b to be maintained is reduced so that the maintenance of the claws 41a and 41b can be easily performed. Further, in the present embodiment, it is related to the circumferential direction between the plurality of claws 41a for forming the crimped portion 40a on the front side in the axial direction and the plurality of claws 41b for forming the crimped portion 40b on the rear side in the axial direction. The phases of the arrangement are different from each other. This facilitates the assembly of equipment for forming a pair of caulked portions 40a, 40b.
[0053]
　In the structure of the present embodiment, for example, the following specifications can be adopted (see FIGS. 11 and 13).
　　Depth dimension y1: 0.45 mm
　　Depth dimension y2: 0.4 mm
　　Tilt angle θ1: 60 degrees
　　Tilt angle θ2: 40 degrees
　　Axial spacing L1: 1.7 mm
　Other configurations and actions are the cases of the first embodiment. Is similar to.
[0054]
　The present invention is not limited to the above-described embodiment, and can be appropriately modified or improved.
　For example, when the present invention is carried out, the circumferential grooves with which the crimped portion of the torque detection sleeve engages may be provided at three or more axial directions on the outer peripheral surface of the torque transmission shaft.
　Further, the number of claws for forming the crimped portion on the torque detection sleeve can be different for each axial portion forming the crimped portion.
[0055]
　The torque detection device of the present invention is not limited to the electric power steering device, and can be used by incorporating it into various mechanical devices.
　When the torque detection device of the present invention is incorporated into an electric power steering device and used, the torque detection device may be installed not only at the front end of the steering shaft but also at an appropriate position such as an input portion of the steering gear unit. it can.
[0056]
　This application is based on a Japanese patent application filed on August 3, 2018 (Japanese Patent Application No. 2018-146419), the contents of which are incorporated herein by reference.
Code description
[0057]
　1 Steering wheel
　2, 2a Steering shaft
　3, 3a Steering column
　4a, 4b 　Universal joint
　5 Intermediate shaft
　6 Steering gear unit
　7 Pinion shaft
　8 Rack shaft
　9 Tie rod
　10,
10a Housing 11, 11a Electric motor
　12 Output shaft
　13 Torsion bar
　14, 14a Torque detection sleeve
　15 Torque detection coil unit
　16 Board
　17 Warm reducer
　18 Inner column
　19 Outer column
　20 Support bracket
　21, 21a Lower shaft
　22 Upper shaft
　23 Lid
　24 Main body
　25 Ball bearing
　26 Ball bearing
　27 Pin
　28 Spline hole
　29,29a tubular portion
　30 female stopper portion
　31 teeth
　32 male stopper portion
　33 groove
　34 torque detecting concave and convex portion
　35 the groove
　36a, 36b windows
　37 axial groove
　38, 38a, 38b circumferential groove
　39 positioning projection
　40,40a , 40b Caulking part
　41 Claw
　42a, 42b Coil
　43 Warm wheel
　44 Warm
　45, 45a, 45b Bottom surface
　46, 46a, 46b Inner surface
The scope of the claims
[Claim 1]
　A torque transmission shaft and
　a cylindrical torque detection sleeve having a plurality of window holes on one side in the axial direction are provided, and the
　torque transmission shaft is formed in each of a plurality of axial directions on the outer peripheral surface in the circumferential direction. The
　torque detection sleeve has circumferential grooves parallel to each other, and the torque detection sleeve is fitted onto the torque transmission shaft so that the other side portion in the axial direction covers the entire circumferential groove, and the circumference thereof. A
　torque detecting device having a crimped portion crimped to the circumferential groove in an axial portion overlapping each of the directional grooves in the radial direction .
[Claim 2]

　The torque detection device according to claim 1 　, wherein each of the circumferential grooves has the same shape as each other .
[Claim 3]

　The torque detection device according to claim 1, 　wherein at least one of the circumferential grooves has a shape different from that of the other circumferential grooves .
[Claim 4]
　The circumferential groove includes an outer opening groove in which a pair of inner side surfaces located on both sides in the axial direction are inclined in a direction away from each other with respect to the axial direction toward the outer side in the radial direction. The
　torque detection device according to any one of claims 1 to 3 , wherein the caulking portion is in contact with each of the inner surfaces of the above .
[Claim 5]

　The torque detection device according to claim 4, 　wherein the inclination angle of the pair of inner surfaces with respect to the central axis of the circumferential groove is 50 degrees to 70 degrees .
[Claim 6]
　The torque transmission shaft is provided with a plurality of axial grooves at a plurality of locations in the circumferential direction of the outer peripheral surface, and the
　torque detection sleeve is provided at a plurality of locations having the same phase as the axial groove on the other side portion in the axial direction. 　The torque detection device according to any one of claims 1 to 5, which has a positioning convex portion protruding inward in the radial direction, and the
　positioning convex portion is provided on one side in the axial direction with respect to the caulking portion.
..
[Claim 7]
　The method for assembling a torque detection device according to any one of claims 1 to 6,
　wherein the other side portion of the torque detection sleeve in the axial direction covers the entire circumferential groove. The step of outer fitting to the torque transmission shaft and the axial portion of the
　torque detection sleeve that overlaps the circumferential groove in the radial direction are arranged in the circumferential direction on the radial outer side of the axial portion. A step of forming the crimped portion in the axial portion by arranging the plurality of claws and pressing the axial portion from the radial outer side to the radial inner side by the plurality of claws.
　How to assemble the torque detector.
[Claim 8]

　7. Claim 7 　in the step of forming the caulking portion, the work of forming the caulking portion for each of the axial portions is performed in order from the axial portion close to one axial side portion of the torque detection sleeve. The method for assembling the torque detection device according to the above.
[Claim 9]
　The
　method for assembling a torque detection device according to claim 7 or 8 , wherein in the step of forming the crimped portion, the number of the claws for forming the crimped portion is made equal for each of the axial portions .
[Claim 10]
　The
　method for assembling a torque detection device according to claim 9 , wherein in the step of forming the crimped portion, the phases of arrangement of the claws for forming the crimped portion in the circumferential direction are matched for each of the axial portions. ..
[Claim 11]
　The
　method for assembling a torque detection device according to claim 9 , wherein in the step of forming the crimped portion, the phase of the arrangement of the claws for forming the crimped portion with respect to the circumferential direction is made different for each of the axial portions. ..
[Claim 12]
　The
　method for assembling a torque detection device according to claim 7 or 8 , wherein in the step of forming the crimped portion, the number of the claws for forming the crimped portion is made different for each of the axial portions .
[Claim 13]
　An electric power steering device including the torque detection device according to any one of claims 1 to 6.