Thin-walled cylindrical sleeve and torque sensor

Abstract

To achieve both ease of press-fitting of a shaft member and ensuring strength against press-fitting.SOLUTION: A thin cylindrical sleeve 30 is formed by: bending a thin plate 38 into a cylindrical shape: extending a butting portion 40 of the thin plate 38 in the circumferential direction of the cylinder in the axial direction of the cylinder: and welding the butting portion 40 with a plurality of welding portions 50. At a position near one end 31 in the axial direction on an inner peripheral surface 33, there is a tapered portion 34 formed so that the plate thickness becomes thinner as it approaches the end 31 in the axial direction. Of the plurality of welding portions 50, an end welded portion 51, which is the welded portion 50 closest to the end portion 31, overlaps at least a portion of the tapered portion 34 in the axial direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a thin-walled cylindrical sleeve and a torque sensor. [Background technology]

[0002] A torque sensor that detects torque applied to a rotating body is attached to the rotating body and is able to detect torque by detecting the angular displacement of the rotating body in the rotational direction when rotational torque acts on the rotating body. For example, in the torque sensor described in Patent Document 1, the rotor disk that is the object of detection by the detection circuit is attached to a shaft member by a sleeve that is a cylindrical support structure. This allows the torque sensor to detect the angular displacement of the rotating body, or shaft member, in the rotational direction via the rotor disk using the detection circuit, and thus detect the torque acting on the shaft member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent Application Publication No. 2383558 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, there are various methods for manufacturing a thin-walled cylindrical sleeve, such as a sleeve to be attached to a shaft member, which is a rotating body. One example of a method for manufacturing a thin-walled cylindrical sleeve at low manufacturing costs is to roll a substantially rectangular thin plate into a cylindrical shape and then laser-weld the butt joints to form a cylindrical shape. In a torque sensor, a shaft member is press-fitted into the thin-walled cylindrical sleeve thus formed, thereby positioning the thin-walled cylindrical sleeve at a desired position on the shaft member. When press-fitting the shaft member into the thin-walled cylindrical sleeve, a tapered portion is typically formed on the inner circumferential surface of the end of the thin-walled cylindrical sleeve that is the side where the shaft member is inserted, to facilitate insertion of the shaft member into the thin-walled cylindrical sleeve.

[0005] However, when a shaft member is press-fitted into a thin-plate cylinder manufactured by laser welding the butt joints of rolled thin plates, the tensile stress acting on the thin-plate cylinder during press-fitting can cause the welded portion to fracture. In particular, when a tapered portion is formed on the inner circumferential surface of the end of a thin-walled cylindrical sleeve, laser welding during manufacture of the thin-walled cylindrical sleeve is performed at a location other than the tapered portion where the plate thickness is thicker than the tapered portion to ensure weld strength. Therefore, the laser welded portion is spaced apart from the axial end of the thin-walled cylindrical sleeve. However, if the welded portion is spaced apart from the end of the thin-walled cylindrical sleeve, stress concentration due to tensile stress acting on the thin-walled cylinder during press-fitting is likely to occur near the welded portion, making the thin-walled cylindrical sleeve more likely to fracture at the welded portion. Thus, it has been very difficult to achieve both ease of press-fitting and sufficient strength against press-fitting in a thin-plate cylinder into which a shaft member is press-fitted.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a thin-walled cylindrical sleeve and a torque sensor that can achieve both ease of press-fitting of an axial member and ensuring strength against press-fitting. [Means for solving the problem]

[0007] The thin-walled cylindrical sleeve of the present disclosure is a thin-walled cylindrical sleeve formed by bending a thin plate into a cylindrical shape and welding the butt joints of the thin plate in the circumferential direction of the cylinder with a plurality of welds, and has a tapered portion on the inner surface located near one end in the axial direction of the cylinder, where the plate thickness becomes thinner as it approaches the end in the axial direction, and of the plurality of welds, the end weld, which is the weld located closest to the end, at least partially overlaps with the tapered portion in the axial direction.

[0008] According to this configuration, the end weld is formed at a position in the axial direction of the thin-walled cylindrical sleeve where at least a portion of the weld overlaps with the tapered portion. Therefore, when a shaft member is press-fitted into the thin-walled cylindrical sleeve from the end where the tapered portion is formed, excessive stress at the end weld can be prevented, thereby preventing stress concentration. Therefore, a decrease in the strength of the thin-walled cylindrical sleeve due to large stress concentration occurring when the shaft member is press-fitted into the thin-walled cylindrical sleeve can be prevented. As a result, it is possible to achieve both ease of press-fitting the shaft member and ensure strength against press-fitting.

[0009] In a preferred embodiment, the end welded portion is located on the inner peripheral surface of the thin-walled cylindrical sleeve on the opposite side of the tapered portion in the axial direction from the side on which the end is located.

[0010] According to this configuration, the end weld is located on the inner circumferential surface of the thin-walled cylindrical sleeve on the opposite side of the tapered portion from the end of the thin-walled cylindrical sleeve in the axial direction, preventing the end weld from being exposed to the tapered portion and preventing the end weld from protruding from the tapered portion. This prevents the shaft member from getting caught on the end weld when press-fitting the shaft member into the thin-walled cylindrical sleeve, allowing for smooth press-fitting. As a result, it is possible to achieve both ease of press-fitting the shaft member and ensure strength against press-fitting.

[0011] In a preferred form, the butt joint is formed by combining a straight portion extending in the axial direction and a curved portion curved circumferentially of the cylinder relative to the axial direction, and the butt joint is formed by the straight portion extending from the end portion, and a sub-weld portion, which is a weld portion different from the end weld portion, is located at the position where the straight portion extending from the end portion intersects with the curved portion.

[0012] With this configuration, the auxiliary weld is located at the position where the straight portion and the curved portion of the butt joint intersect, which increases the joint strength at the position where a large force is applied to the butt joint, thereby improving the strength of the thin-walled cylindrical sleeve against press-fitting of the shaft member. As a result, it is possible to achieve both ease of press-fitting of the shaft member and ensure strength against press-fitting.

[0013] In a preferred embodiment, the welded portion is formed such that a plurality of the welded portions are stacked in the circumferential direction or the axial direction of the cylinder, or in an elongated shape in the circumferential direction or the axial direction of the cylinder.

[0014] According to this configuration, since the multiple welds are overlapped in the circumferential direction of the cylinder or are formed in an elongated shape in the circumferential direction of the cylinder, even if the positions of the welds are shifted circumferentially from the intended positions, the butt joints can be joined by the welds. This ensures strength when the shaft member is press-fitted into the thin-walled cylindrical sleeve. Furthermore, since the multiple welds are overlapped in the axial direction of the cylinder or are formed in an elongated shape in the axial direction of the cylinder, the joining strength between the butt joints by the welds can be increased. This ensures strength when the shaft member is press-fitted into the thin-walled cylindrical sleeve.

[0015] The torque sensor of the present disclosure comprises a shaft member that transmits rotational torque, a thin-walled cylindrical sleeve formed in a substantially cylindrical shape and into which the shaft member is press-fitted, a detection member that is arranged around the thin-walled cylindrical sleeve, and a detection coil that detects movement of the detection member in a circumferential direction around the shaft member, wherein the thin-walled cylindrical sleeve is formed by bending a thin plate into a cylindrical shape, and the butt joints of the thin plate in the circumferential direction of the cylinder are welded with a plurality of welds, and the thin-walled cylindrical sleeve has a tapered portion on its inner surface located near one end in the axial direction of the cylinder, the plate thickness becoming thinner as it approaches the end in the axial direction, and of the plurality of welds, the end weld, which is the weld located nearest to the end, at least a portion of which overlaps with the tapered portion in the axial direction.

[0016] According to this configuration, the end weld is formed at a position in the axial direction of the thin-walled cylindrical sleeve where at least a portion of the weld overlaps with the tapered portion. Therefore, when a shaft member is press-fitted into the thin-walled cylindrical sleeve from the end where the tapered portion is formed, excessive stress at the end weld can be prevented, thereby preventing stress concentration. Therefore, a decrease in the strength of the thin-walled cylindrical sleeve due to large stress concentration occurring when the shaft member is press-fitted into the thin-walled cylindrical sleeve can be prevented. As a result, it is possible to achieve both ease of press-fitting the shaft member and ensure strength against press-fitting. [Effects of the Invention]

[0017] The thin-walled cylindrical sleeve and torque sensor according to the present disclosure have the advantage of being able to easily press-fit a shaft member while also ensuring sufficient strength against press-fitting. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a steering device according to an embodiment. [Figure 2] FIG. 2 is a perspective view of a main part of the steering device according to the embodiment. [Figure 3]FIG. 3 is a perspective view of the torque sensor, the stub shaft, and the pinion gear. [Figure 4] FIG. 4 is a perspective view of the main components of the torque sensor shown in FIG. [Figure 5] FIG. 5 is an explanatory diagram showing a state in which the input rotor is attached to the stub shaft. [Figure 6] FIG. 6 is a perspective view of a thin cylindrical sleeve of the input rotor shown in FIG. [Figure 7] FIG. 7 is a plan view of a thin plate used to manufacture the thin cylindrical sleeve shown in FIG. [Figure 8] FIG. 8 is a detailed view of part C in FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along the line E-E in FIG. [Figure 10] FIG. 10 is a cross-sectional view showing a state in which the input rotor is attached to the stub shaft. [Figure 11] FIG. 11 is an explanatory view showing a modified example of the thin-walled cylindrical sleeve according to the embodiment, in which two end welded portions are overlapped in the circumferential direction. [Figure 12] FIG. 12 is an explanatory view showing a modified example of the thin-walled cylindrical sleeve according to the embodiment, in which the end welded portion is formed in a circumferentially elongated shape. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the following modes for carrying out the invention (hereinafter referred to as embodiments). Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0020] [Embodiment] Fig. 1 is a schematic diagram of a steering device 80 according to an embodiment. As shown in Fig. 1, the steering device 80 includes, in the order in which a force applied by an operator is transmitted, a steering wheel 81, a steering shaft 82, a universal joint 84, a lower shaft 85, a universal joint 86, a stub shaft 87, a steering gear 88, and a tie rod 89. The steering device 80 also includes a control device (hereinafter referred to as an ECU (Electronic Control Unit)) 90, a torque sensor 10, and an electric motor 92. A vehicle speed sensor 91 is provided in the vehicle and outputs a vehicle speed signal V to the ECU 90 via CAN (Controller Area Network) communication.

[0021] The steering shaft 82 is connected to the steering wheel 81 at one end and to a universal joint 84 at the other end.

[0022] Lower shaft 85 is connected at one end to universal joint 84 and at the other end to universal joint 86. Stub shaft 87 is connected at one end to universal joint 86 and at the other end to torque sensor 10. Torque sensor 10 is connected at one end to stub shaft 87 and at the other end to pinion gear 88a of steering gear 88.

[0023] More specifically, the stub shaft 87 and the pinion gear 88a are connected via a torsion bar (not shown). One end of the torsion bar is connected to the stub shaft 87, and the other end is connected to the pinion gear 88a, and the torsion bar transmits rotational torque between the stub shaft 87 and the pinion gear 88a. The torque sensor 10 detects the rotational torque transmitted between the stub shaft 87 and the pinion gear 88a via the torsion bar.

[0024] The steering gear 88 includes a pinion gear 88a and a rack bar 88b. The pinion gear 88a is connected to the stub shaft 87 via a torsion bar. One end of the pinion gear 88a is connected to the torque sensor 10, and the other end is capable of transmitting the driving force of the electric motor 92. The rack bar 88b meshes with the pinion gear 88a. The steering gear 88 converts the rotational motion transmitted to the pinion gear 88a into linear motion by the rack bar 88b. The tie rod 89 is connected to the rack bar 88b. In other words, the steering device 80 is of a rack-and-pinion type.

[0025] 2 is a perspective view of a main portion of a steering device 80 according to an embodiment. The pinion gear 88a is disposed in a pinion housing 88s. The rack bar 88b is disposed in a rack housing 88h formed integrally with the pinion housing 88s. A motor mounting portion 88m for mounting an electric motor 92 is formed in the pinion housing 88s, and the electric motor 92 is mounted to the motor mounting portion 88m. The driving force generated by the electric motor 92 can be transmitted to the pinion gear 88a within the pinion housing 88s. The torque sensor 10 is attached to the pinion housing 88s, and is coupled to both the stub shaft 87 and the pinion gear 88a disposed within the pinion housing 88s.

[0026] The torque sensor 10 detects the steering force of the driver transmitted to the steering shaft 82 via the steering wheel 81 as a steering torque. The vehicle speed sensor 91 detects the traveling speed (vehicle speed) of the vehicle on which the steering device 80 is mounted. The electric motor 92, the torque sensor 10, and the vehicle speed sensor 91 are electrically connected to the ECU 90.

[0027] The ECU 90 controls the operation of the electric motor 92. The ECU 90 also acquires signals from the torque sensor 10 and the vehicle speed sensor 91. That is, the ECU 90 acquires the steering torque T from the torque sensor 10 and acquires the vehicle speed signal V from the vehicle speed sensor 91. When an ignition switch 98 is in the on state, the ECU 90 is supplied with power from a power supply device (for example, an on-board battery) 99. The ECU 90 calculates an assist steering command value of the assist command based on the steering torque T and the vehicle speed signal V. The ECU 90 then adjusts the power value X to be supplied to the electric motor 92 based on the calculated assist steering command value. The ECU 90 acquires, as operation information Y, information on an induced voltage from the electric motor 92 or information output from a rotation detection device such as a resolver provided in the electric motor 92.

[0028] The steering force of the operator (driver) input to the steering wheel 81 is detected as steering torque T by torque sensor 10. ECU 90 acquires the steering torque T from torque sensor 10 and acquires a vehicle speed signal V from vehicle speed sensor 91. Then, ECU 90 controls the operation of electric motor 92. The driving force generated by electric motor 92 is transmitted to pinion gear 88a as auxiliary steering torque. That is, the steering force of the operator input to the steering wheel 81 is transmitted from stub shaft 87 via a torsion bar, and the auxiliary steering torque is also transmitted from electric motor 92 to pinion gear 88a. Because the auxiliary steering torque is transmitted to pinion gear 88a from electric motor 92, the force required to operate the steering wheel 81 is reduced.

[0029] The steering force transmitted to the pinion gear 88a is transmitted to the tie rod 89 via the steering gear 88, displacing the wheels.

[0030] 3 is a perspective view of the torque sensor 10, the stub shaft 87, and the pinion gear 88a. The stub shaft 87 and the pinion gear 88a are connected to the torque sensor 10 from opposite sides of the torque sensor 10. In other words, the stub shaft 87 and the pinion gear 88a are disposed on opposite sides of the torque sensor 10, and extend in opposite directions.

[0031] Of these, the pinion gear 88a is formed with a gear portion 88ag that meshes with teeth (not shown) formed on the rack bar 88b. Furthermore, the pinion gear 88a is formed with a spline 88as at an end opposite to the end connected to the torque sensor 10, to which a worm wheel (not shown) is attached that meshes with a worm gear (not shown) attached to the output shaft of the electric motor 92. As a result, auxiliary steering torque from the electric motor 92 is transmitted to the pinion gear 88a via the worm gear and worm wheel.

[0032] Fig. 4 is a perspective view of the main components of the torque sensor 10 shown in Fig. 3. The torque sensor 10 has an input rotor 20 attached to an input shaft, which is one of the shaft members connected to the torque sensor 10, an output rotor 70 attached to an output shaft, which is the other shaft member, and a printed circuit board 15 on which a detection coil 16 is disposed. In this embodiment, the input shaft is a stub shaft 87, and the input rotor 20 is attached to the stub shaft 87. The output shaft is a pinion gear 88a, and the output rotor 70 is attached to the pinion gear 88a.

[0033] The input rotor 20 has a thin cylindrical sleeve 30 formed in a substantially cylindrical shape, and a vane-shaped member 65 serving as a detection member disposed around the thin cylindrical sleeve 30. The thin cylindrical sleeve 30 is made of a metal material, and its inner diameter is approximately the same as the outer diameter of the stub shaft 87 at the position where the input rotor 20 is attached. Therefore, the input rotor 20 is attached to the stub shaft 87 by press-fitting the stub shaft 87 into the thin cylindrical sleeve 30.

[0034] The blade-shaped member 65 is a thin plate-like member made of a metal material, and is arranged around the thin-walled cylindrical sleeve 30 with the thickness direction of the plate oriented in the axial direction of the thin-walled cylindrical sleeve 30. The blade-shaped member 65 has a plurality of blade pieces spaced apart from one another in the circumferential direction of the thin-walled cylindrical sleeve 30, and is formed by arranging the plurality of blade pieces around the thin-walled cylindrical sleeve 30. The thin-walled cylindrical sleeve 30 and the blade-shaped member 65 are integrally formed by a resin mold 60 made of a resin material. In other words, the blade-shaped member 65 is arranged around the thin-walled cylindrical sleeve 30 by the resin mold 60.

[0035] The vane-shaped members 65 of the input rotor 20 are disposed near one end of the input rotor 20 in the axial direction of the thin-walled cylindrical sleeve 30. The input rotor 20 is attached to the stub shaft 87 with the side on which the vane-shaped members 65 are disposed facing the side on which the output rotor 70 is located.

[0036] The output rotor 70 has a sleeve portion 71 formed in a substantially cylindrical shape and a vane-shaped member 72 serving as a detection member that is disposed around the sleeve portion 71. The sleeve portion 71 is made of a metal material, and its inner diameter is approximately the same as the outer diameter of the pinion gear 88a at the position where the output rotor 70 is attached. Therefore, the output rotor 70 is attached to the pinion gear 88a by press-fitting the pinion gear 88a into the sleeve portion 71.

[0037] The blade-shaped member 72 is a thin plate-like member made of a metal material, and is arranged around the sleeve portion 71 with the thickness direction of the plate oriented in the axial direction of the sleeve portion 71. The blade-shaped member 72 has a plurality of blade pieces spaced apart from one another in the circumferential direction of the sleeve portion 71, and is formed by arranging the plurality of blade pieces around the sleeve portion 71.

[0038] The vane-shaped members 72 of the output rotor 70 and the vane-shaped members 65 of the input rotor 20 differ in the circumferential size of each vane and the circumferential spacing between the vanes. In this embodiment, the vane-shaped members 72 of the output rotor 70 are larger in circumferential size and the circumferential spacing between the vanes are also larger than those of the vane-shaped members 65 of the input rotor 20. Unlike the input rotor 20, the sleeve portion 71 and the vane-shaped members 72 of the output rotor 70 are integrally formed as a single member made of a metal material.

[0039] The vane-shaped members 72 of the output-side rotor 70 are disposed near one end of the output-side rotor 70 in the axial direction of the sleeve portion 71. The output-side rotor 70 is attached to the pinion gear 88a in such a manner that the side on which the vane-shaped members 72 are disposed faces the side on which the input-side rotor 20 is located.

[0040] The printed circuit board 15 is disposed between the input rotor 20 and the output rotor 70. A detection coil 16 is disposed on the printed circuit board 15 to detect movement of the vane-shaped members 65 of the input rotor 20 in the circumferential direction about the stub shaft 87, and movement of the vane-shaped members 72 of the output rotor 70 in the circumferential direction about the pinion gear 88a. The detection coil 16 is disposed in a position facing the vane-shaped members 65 of the input rotor 20 and the vane-shaped members 72 of the output rotor 70.

[0041] The detection coil 16 is configured so that its inductance changes when the relative circumferential position of the vane-shaped members 65 of the input rotor 20 and the vane-shaped members 72 of the output rotor 70 changes. Thus, by detecting the change in inductance of the detection coil 16, the torque sensor 10 can detect a relative circumferential angular change between the stub shaft 87 to which the input rotor 20 is attached and the pinion gear 88a to which the output rotor 70 is attached. Because rotational torque is transmitted between the stub shaft 87 and the pinion gear 88a via a torsion bar, the torque sensor 10 can detect the torque transmitted between the stub shaft 87 and the pinion gear 88a by detecting the relative angular change between the stub shaft 87 and the pinion gear 88a.

[0042] FIG. 5 is an explanatory diagram showing the input rotor 20 attached to the stub shaft 87. Note that the vane-shaped members 65 of the input rotor 20 are omitted from the illustration in FIG. 5. The resin mold 60 of the input rotor 20 has a sleeve support portion 60a that supports the thin-walled cylindrical sleeve 30 and a vane-shaped member support portion 60b that supports the vane-shaped members 65. The sleeve support portion 60a is disposed radially outward of the thin-walled cylindrical sleeve 30 and has a support member that extends in the axial direction of the thin-walled cylindrical sleeve 30 along the outer peripheral surface of the thin-walled cylindrical sleeve 30. The sleeve support portion 60a has a plurality of support members that are arranged side by side in the circumferential direction.

[0043] The blade-shaped member support portion 60b is formed in a flange shape in the resin mold 60, and is formed around the entire circumference in the circumferential direction with the thickness direction of the flange oriented in the axial direction of the thin-walled cylindrical sleeve 30. The blade-shaped member 65 is attached to the blade-shaped member support portion 60b formed in this way, and is supported by the blade-shaped member support portion 60b.

[0044] The input side rotor 20 has a resin mold 60 attached to the thin-walled cylindrical sleeve 30 in a positional relationship in which the blade-shaped member support portion 60b is located near one end of the thin-walled cylindrical sleeve 30 in the axial direction, and the resin mold 60 and the thin-walled cylindrical sleeve 30 are formed integrally.

[0045] FIG. 6 is a perspective view of the thin-walled cylindrical sleeve 30 of the input rotor 20 shown in FIG. 5 . The thin-walled cylindrical sleeve 30 is a metal member formed in a substantially cylindrical shape. The thin-walled cylindrical sleeve 30 has a tapered portion 34 formed on its inner circumferential surface 33 near one end 31 in the axial direction of the thin-walled cylindrical sleeve 30. The tapered portion 34 formed on the inner circumferential surface 33 of the thin-walled cylindrical sleeve 30 is inclined so that the thickness becomes thinner as it approaches the end 31 in the axial direction of the thin-walled cylindrical sleeve 30. Specifically, the input rotor 20 is attached to the stub shaft 87 by press-fitting the stub shaft 87 into the thin-walled cylindrical sleeve 30. The tapered portion 34 is formed on the inner circumferential surface 33 of the thin-walled cylindrical sleeve 30 on the side where the end 31, into which the stub shaft 87 is press-fitted, is located.

[0046] Fig. 7 is a plan view of a thin plate 38 used in manufacturing the thin-walled cylindrical sleeve 30 shown in Fig. 6. The thin-walled cylindrical sleeve 30 is formed by bending the thin plate 38 into a cylindrical shape. The thin plate 38 is formed in a strip shape, and the thin-walled cylindrical sleeve 30 is formed by bending the thin plate 38 so that the longitudinal direction of the thin plate 38 is the circumferential direction of the cylinder.

[0047] The thin-walled cylindrical sleeve 30 is formed by butting ends of the thin plates 38 located on both sides in the longitudinal direction together in the circumferential direction as butt joints 40, and welding is performed at welds 50. Therefore, in the thin-walled cylindrical sleeve 30 formed in a substantially cylindrical shape, the butt joints 40 of the thin plates 38 in the circumferential direction of the cylinder are formed to extend in the axial direction of the cylinder. In this embodiment, the welds 50 for welding the butt joints 40 are laser welded, and the butt joints 40 are welded at a plurality of welds 50.

[0048] Of the multiple welds 50 that weld the butt joint 40, the end weld 51, which is the weld 50 located closest to the end 31 on the side where the tapered portion 34 is formed, has at least a portion that overlaps with the tapered portion 34 in the axial direction of the thin-walled cylindrical sleeve 30.

[0049] The butt joint 40 is formed by combining a straight portion 41 extending in the axial direction of the cylinder, which is the shape of the thin-walled cylindrical sleeve 30, with a curved portion 42 curved in the circumferential direction of the cylinder relative to the axial direction. More specifically, the butt joint 40 located at one end in the longitudinal direction of the thin plate 38 is curved at the curved portion 42, thereby forming a convex portion 43 that is convex toward the side opposite to the side where the other end in the longitudinal direction is located. The convex portion 43 is formed to be convex in the longitudinal direction of the thin plate 38, and is formed to have a portion that is convex in the direction in which the width of the thin plate 38 in the width direction becomes larger than the base of the convex portion 43.

[0050] On the other hand, the abutment portion 40 located on the other end side in the longitudinal direction of the thin plate 38 is curved at the curved portion 42, and thereby has a recessed portion 44 recessed toward the side where the one end in the longitudinal direction is located. The recessed portion 44 is formed to be recessed in the longitudinal direction of the thin plate 38, and also has a portion formed to be recessed in a direction where the width in the width direction of the thin plate 38 becomes larger than the position of the end of the thin plate 38 in the recessed portion 44. The protrusions 43 and recessed portions 44 formed in this way are formed to be substantially the same shape.

[0051] The convex portions 43 and the concave portions 44 are formed at the same positions in the width direction of the thin plate 38, i.e., in the axial direction of the cylinder that is the shape of the thin-walled cylindrical sleeve 30. As a result, when the thin plate 38 is formed into a cylindrical shape by butting the butted portions 40 together, the convex portion 43 formed on one butted portion 40 fits into the concave portion 44 formed on the other butted portion 40, and the butted portions 40 are joined together.

[0052] At this time, the protrusion 43 has a portion that is protruding in a direction in which the width in the width direction of the thin plate 38 becomes larger than the base of the protrusion 43, and the recess 44 has a portion that is recessed in a direction in which the width in the width direction of the thin plate 38 becomes larger than the position of the end of the thin plate 38 at the recess 44. Therefore, when the protrusion 43 fits into the recess 44, the protrusion 43 cannot be removed from the recess 44 in the circumferential direction of the thin-walled cylindrical sleeve 30, and the protrusion 43 and the recess 44 are combined.

[0053] In this embodiment, two convex portions 43 and two concave portions 44 are formed in this manner, that is, two sets of corresponding convex portions 43 and concave portions 44 are formed in the butt joint 40. Welds 50 that join the butt joints 40 are applied at multiple locations in a state in which the convex portions 43 fit into the concave portions 44 and the butt joints 40 are butted together. The welds 50 are applied, for example, at positions in the butt joint 40 where the convex portions 43 and the concave portions 44 are combined, or at positions on both sides of the convex portions 43 and the concave portions 44 in the axial direction of the thin-walled cylindrical sleeve 30.

[0054] 8 is a detailed view of portion C in FIG. 6. The butt joint 40 has a straight portion 41 and a curved portion 42, and is formed by extending the straight portion 41 from the end portion 31. Of the multiple welds 50, the end weld 51, which is applied at a position that at least partially overlaps the tapered portion 34 formed on the inner circumferential surface 33 of the thin-walled cylindrical sleeve 30, is applied at the position of the straight portion 41 in the butt joint 40. In the butt joint 40, a sub-weld 52, which is a weld 50 different from the end weld 51, is located at the position where the straight portion 41, which extends from the end portion 31 and to which the end weld 51 is applied, intersects with the curved portion 42. In other words, the sub-weld 52 is applied to the straight portion 41 to which the end weld 51 is applied, at the end of the straight portion 41 that is connected to the curved portion 42.

[0055] Here, the weld 50 may be welded with a small gap in the circumferential direction between the butt joints 40. In this case, it is preferable that the end weld 51 be formed so that the weld position A, which is the distance from the end 31 to the end weld 51, is within a predetermined range with respect to the weld gap G, which is the gap between the butt joints 40. Specifically, when the weld gap G is formed, the weld position A is determined according to the weld gap G so that it satisfies a stress concentration factor calculated from the stress generated in the thin-walled cylindrical sleeve 30 when the stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30 and the allowable stress of the material forming the thin-walled cylindrical sleeve 30.

[0056] Fig. 9 is an E-E cross-sectional view of Fig. 8. End weld 51, at least a portion of which is arranged at a position overlapping tapered portion 34, is located on the inner circumferential surface 33 of thin-walled cylindrical sleeve 30 on the opposite side of tapered portion 34 from the side where end 31 is located in the axial direction of thin-walled cylindrical sleeve 30.

[0057] In other words, when viewed in the cross-sectional direction of the plate forming the thin-walled cylindrical sleeve 30, the end weld 51 decreases in size from the end weld outer surface 51a, which is the portion of the end weld 51 located on the outer peripheral surface 32 of the thin-walled cylindrical sleeve 30, to the end weld inner surface 51b, which is the portion of the end weld 51 located on the inner peripheral surface 33 of the thin-walled cylindrical sleeve 30.

[0058] In the end weld 51 formed in this manner, the welding position A, which is the distance from the end 31 of the thin-walled cylindrical sleeve 30 to the end weld outer surface 51a, is less than the distance L from the end 31 of the thin-walled cylindrical sleeve 30 to the tapered portion end 34a, which is the end of the tapered portion 34 opposite to the side where the end 31 of the thin-walled cylindrical sleeve 30 is located. In other words, the welding position A, which is the distance from the end 31 of the thin-walled cylindrical sleeve 30 to the end weld outer surface 51a, satisfies the relationship A≦L with respect to the distance L from the end 31 of the thin-walled cylindrical sleeve 30 to the tapered portion end 34a.

[0059] Therefore, if the range in the axial direction of the thin-walled cylindrical sleeve 30 on the end 31 side of the thin-walled cylindrical sleeve 30 from the tapered portion end 34a is defined as range α, and the range on the opposite side of the tapered portion end 34a to the side where the end 31 of the thin-walled cylindrical sleeve 30 is located is defined as range β, the outer surface 51a of the end weld overlaps with range α.

[0060] Furthermore, the distance B from the end 31 of the thin-walled cylindrical sleeve 30 to the end weld inner surface 51b of the end weld 51 is equal to or greater than the distance L from the end 31 of the thin-walled cylindrical sleeve 30 to the tapered portion end 34a. In other words, the distance B from the end 31 of the thin-walled cylindrical sleeve 30 to the end weld inner surface 51b satisfies the relationship B≧L with respect to the distance L from the end 31 of the thin-walled cylindrical sleeve 30 to the tapered portion end 34a. Therefore, the end weld outer surface 51a overlaps with the range β but does not overlap with the range α.

[0061] Next, the procedure for assembling the stub shaft 87 to the thin-walled cylindrical sleeve 30 of the input rotor 20 of the torque sensor 10 will be described. Note that the procedure described below is an example of a manufacturing process, and the order of the manufacturing process can be changed as desired. The thin-walled cylindrical sleeve 30 has a strip-shaped thin plate 38 with butt joints 40 at both ends in the length direction, and a straight portion 41 and a curved portion 42 form a convex portion 43 at one butt joint 40, and a concave portion 44 at the other butt joint 40. In addition, a tapered portion 34 is formed at one end 31 in the width direction of the thin plate 38.

[0062] After forming the convex portions 43 and concave portions 44 and the tapered portion 34, the thin plate 38 is bent into a cylindrical shape so that the length direction of the thin plate 38 becomes the circumferential direction and the surface on which the tapered portion 34 is formed becomes the inner circumferential surface 33, and the convex portions 43 are inserted into the concave portions 44 so that the butt joints 40 are butted together. After the butt joints 40 are butted together, the butt joints 40 are welded together using multiple welds 50. At this time, the end weld 51 located closest to the end 31 is positioned so that at least a portion of it overlaps with the tapered portion 34 in the axial direction of the cylinder. In this way, by bending the thin plate 38 into a cylindrical shape and butting the butt joints 40 together and welding them together using multiple welds 50, a thin-walled cylindrical sleeve 30 with a substantially cylindrical shape is formed.

[0063] FIG. 10 is a cross-sectional view showing the input rotor 20 attached to the stub shaft 87. After the thin-walled cylindrical sleeve 30 is formed, the thin-walled cylindrical sleeve 30 and the vane-shaped members 65, which are manufactured in a separate process, are integrally formed using a resin mold 60. That is, the thin-walled cylindrical sleeve 30 and the vane-shaped members 65 are aligned, and then the resin mold 60 is injection-molded. This produces the input rotor 20. In this process, the vane-shaped members 65, which are integrally formed with the thin-walled cylindrical sleeve 30 using the resin mold 60, are positioned axially toward the end 31 of the thin-walled cylindrical sleeve 30 opposite the end 31 on the side where the tapered portion 34 is formed on the inner circumferential surface 33. The input rotor 20 is attached to the stub shaft 87 by press-fitting the stub shaft 87 into the thin-walled cylindrical sleeve 30 of the input rotor 20 manufactured in this manner.

[0064] The stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30 from the end 31 of the thin-walled cylindrical sleeve 30, where the tapered portion 34 is formed on the inner circumferential surface 33. The stub shaft 87 has a press-fit portion 87a, which has an outer diameter substantially the same as the inner diameter of the thin-walled cylindrical sleeve 30 and is press-fitted into the thin-walled cylindrical sleeve 30. The stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30 by inserting the press-fit portion 87a of the stub shaft 87 into the thin-walled cylindrical sleeve 30 from the end 31 of the thin-walled cylindrical sleeve 30, where the tapered portion 34 is formed. The stub shaft 87 can be easily inserted into the inner circumferential surface 33 of the thin-walled cylindrical sleeve 30 by inserting it from the end 31 of the thin-walled cylindrical sleeve 30, where the tapered portion 34 is formed. This allows the stub shaft 87 to be easily press-fitted into the thin-walled cylindrical sleeve 30.

[0065] The end 31 of the thin-walled cylindrical sleeve 30, on the side where the tapered portion 34 is formed, has a plurality of abutment portions 31a (see FIG. 6) that protrude axially and are spaced apart circumferentially. The stub shaft 87 also has a stepped portion 87b formed at a predetermined axial position adjacent to the press-fit portion 87a, which is a stepped portion formed by a change in diameter relative to the press-fit portion 87a. The stub shaft 87, which is press-fitted into the thin-walled cylindrical sleeve 30, is inserted into the thin-walled cylindrical sleeve 30 until the stepped portion 87b abuts against the abutment portion 31a of the thin-walled cylindrical sleeve 30. Thus, the input rotor 20 having the thin-walled cylindrical sleeve 30 and the stub shaft 87 are positioned axially and fixed to each other when the stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30.

[0066] When the thin-walled cylindrical sleeve 30 is press-fitted and fixed to the stub shaft 87, the stub shaft 87 may be inserted into the fixed thin-walled cylindrical sleeve 30, or the thin-walled cylindrical sleeve 30 may be fitted onto the fixed stub shaft 87.

[0067] When the stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30, a force that tends to spread in the circumferential direction acts on the thin-walled cylindrical sleeve 30. This force is concentrated at the weld 50 that joins the butted portions 40, making it easy for stress to concentrate at the weld 50. In particular, stress is likely to concentrate at the end weld 51, which is the weld 50 closest to the end 31 on the side where the stub shaft 87 enters, and the end weld 51 is likely to break.

[0068] Furthermore, when the stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30, a force that tries to expand the thin-walled cylindrical sleeve 30 in the circumferential direction acts on the thin-walled cylindrical sleeve 30 from the position of the end 31. For this reason, as the distance from the end 31 of the thin-walled cylindrical sleeve 30 to the end weld 51 increases, a large stress concentration is likely to occur at the end weld 51, making the thin-walled cylindrical sleeve 30 more likely to break at the position of the end weld 51.

[0069] In contrast, in this embodiment, the end weld 51 is provided at a position in the axial direction of the thin-walled cylindrical sleeve 30 where at least a portion of it overlaps with the tapered portion 34. Therefore, when the stub shaft 87, which is an axial member, is press-fitted from the end 31 of the thin-walled cylindrical sleeve 30 on the side where the tapered portion 34 is formed, excessive stress at the end weld 51 can be prevented, and stress concentration can be suppressed. Therefore, a decrease in the strength of the thin-walled cylindrical sleeve 30 due to large stress concentration occurring when the axial member is press-fitted into the thin-walled cylindrical sleeve 30 can be suppressed. As a result, it is possible to achieve both ease of press-fitting the axial member and ensure strength against press-fitting.

[0070] Furthermore, because the end weld inner surface 51b of the end weld 51 is located on the opposite side of the tapered portion end 34a of the tapered portion 34 from the side where the end 31 of the thin-walled cylindrical sleeve 30 is located, the end weld 51 can be prevented from being exposed to the tapered portion 34. In other words, if the end weld 51 is exposed to the tapered portion 34, the end weld 51 will likely protrude from the tapered portion 34. In this case, when the stub shaft 87 is press-fitted into the thin-walled cylindrical sleeve 30, the end weld 51 will likely get caught on the protruding portion of the tapered portion 34, which could make it difficult to press-fit the stub shaft 87 into the thin-walled cylindrical sleeve 30.

[0071] In contrast, in this embodiment, end weld inner surface 51b of end weld 51 is not located on tapered portion 34, which prevents end weld 51 from being exposed to tapered portion 34 and prevents end weld 51 from protruding from tapered portion 34. This prevents stub shaft 87 from getting caught on end weld 51 when press-fitting stub shaft 87 into thin-walled cylindrical sleeve 30, allowing for smooth press-fitting. As a result, it is possible to achieve both ease of press-fitting of the shaft member and ensure strength against press-fitting.

[0072] Furthermore, because the auxiliary weld 52 is located at the position where the straight portion 41 and the curved portion 42 of the butt joint 40 intersect, the joint strength between the butt joints 40 can be improved. Specifically, the butt joints 40 have protrusions 43 and recesses 44 that prevent the thin-walled cylindrical sleeve 30 from slipping out in the circumferential direction. When a force acts in a direction that causes the protrusion 43 to slip out of the recess 44 in the circumferential direction, this force is likely to act on the intersection of the curved portion 42 forming the protrusion 43 or the recess 44 and the straight portion 41 continuing from the curved portion 42. Therefore, by locating the auxiliary weld 52 at the intersection of the curved portion 42 and the straight portion 41, the joint strength at the butt joint 40 where a large force is applied can be increased, thereby improving the strength of the thin-walled cylindrical sleeve 30 against press-fitting of a shaft member. As a result, it is possible to achieve both ease of press-fitting of the shaft member and sufficient strength against press-fitting.

[0073] [Variations] In the thin-walled cylindrical sleeve 30 according to the embodiment described above, one weld 50 is provided at each welding position. However, multiple welds 50 may be located at a single location. FIG. 11 is an explanatory diagram showing a modified example of the thin-walled cylindrical sleeve 30 according to the embodiment, in which two end welds 51 are overlapped in the circumferential direction. For example, as shown in FIG. 11 , the welds 50 may be arranged so that the two end welds 51 are overlapped in the circumferential direction of the thin-walled cylindrical sleeve 30. By overlapping the two end welds 51 in this way in the circumferential direction of the thin-walled cylindrical sleeve 30, the butt joints 40 can be joined by the welds 50 even if the positions of the end welds 51 are shifted circumferentially from the intended positions. This ensures strength when a shaft member is press-fitted into the thin-walled cylindrical sleeve 30.

[0074] Furthermore, in the thin-walled cylindrical sleeve 30 according to the embodiment described above, the welded portion 50 has substantially the same size in the circumferential direction and in the axial direction of the thin-walled cylindrical sleeve 30. However, the welded portion 50 may have different sizes in the circumferential direction and in the axial direction of the thin-walled cylindrical sleeve 30. FIG. 12 is an explanatory diagram showing a modified example of the thin-walled cylindrical sleeve 30 according to the embodiment, in which the end welded portion 51 is formed in an elongated shape in the circumferential direction. For example, as shown in FIG. 12 , the welded portion 51 may be formed in an elongated shape in the circumferential direction of the thin-walled cylindrical sleeve 30. By forming the end welded portion 51 in an elongated shape in the circumferential direction of the thin-walled cylindrical sleeve 30 in this way, even if the position of the end welded portion 51 is shifted circumferentially from the intended position, the butt portions 40 can be joined by the welded portion 50. This ensures strength when a shaft member is press-fitted into the thin-walled cylindrical sleeve 30.

[0075] Furthermore, in the above-described embodiment, the torque sensor 10 is coupled to the stub shaft 87 and the pinion gear 88a, but the shaft member to which the torque sensor 10 is coupled may be other than the stub shaft 87 or the pinion gear 88a. The torque sensor 10 may be coupled to, for example, the steering shaft 82 to detect the torque acting on the steering shaft 82. Regardless of the shaft member to which the torque sensor 10 is coupled, it is sufficient that the tapered portion 34 is formed on the inner circumferential surface 33 of the thin-walled cylindrical sleeve 30 of the input rotor 20, and that at least a portion of the end weld 51 overlaps with the tapered portion 34 in the axial direction of the thin-walled cylindrical sleeve 30.

[0076] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. The configurations described as the embodiments and modified examples may be combined as appropriate. [Explanation of symbols]

[0077] 10 Torque sensor 15 Printed circuit board 16 detection coil 20 Input rotor 30 Thin-walled cylindrical sleeve 31 End 32 Outer surface 33 Inner peripheral surface 34 Tapered section 34a Tapered end 38 thin plate 40 Butt joint 41 Straight section 42 Curved section 50 Welded Section 51 End weld 51a Outer surface of end weld 51b Inner surface of end weld 52 Sub-weld 60 Resin mold 65 Wing-shaped member 70 Output rotor 80 Steering device 81 Steering wheel 82 Steering shaft 87 Stub shaft 88 Steering Gear 88a pinion gear 88ag gear part 88b Rack Bar 89 tie rod 90 ECU 91 Vehicle speed sensor 92 Electric motor 98 Ignition switch 99 Power supply

Claims

1. A thin-walled cylindrical sleeve formed by bending a thin plate into a cylindrical shape and welding abutting portions of the thin plate in a circumferential direction of the cylindrical shape with a plurality of welds, a tapered portion formed on an inner peripheral surface of the thin-walled cylindrical sleeve on a side where one end in an axial direction of the thin-walled cylindrical sleeve is located, the tapered portion being formed so that the thickness of the tapered portion becomes thinner as the thickness of the tapered portion approaches the end in the axial direction, Among the plurality of welds, an end weld, which is the weld located closest to the end, at least partially overlaps with the tapered portion in the axial direction, The end weld is a distance from the end to an outer surface of the end weld, which is a portion of the end weld located on the outer peripheral surface of the thin-walled cylindrical sleeve, is equal to or less than a distance L from the end to a tapered portion end, which is an end of the tapered portion opposite to the side where the end is located; A thin-walled cylindrical sleeve in which the distance from the end to the inner surface of the end weld, which is the portion of the end weld located on the inner surface of the thin-walled cylindrical sleeve, is equal to or greater than the distance L.

2. 2. The thin-walled cylindrical sleeve according to claim 1, wherein the end weld portion is located on the inner surface of the thin-walled cylindrical sleeve on the opposite side of the tapered portion in the axial direction from the side on which the end portion is located.

3. the abutting portion is formed by combining a linear portion extending in the axial direction and a curved portion curved in a circumferential direction of the thin-walled cylindrical sleeve formed in the cylindrical shape with respect to the axial direction, The butted portion is formed by extending the linear portion from the end portion, 3. The thin-walled cylindrical sleeve according to claim 1, wherein a sub-weld, which is a weld different from the end weld, is located at the position where the straight portion extending from the end intersects with the curved portion.

4. The thin-walled cylindrical sleeve according to any one of claims 1 to 3, wherein the welded portions are stacked in the circumferential direction or the axial direction of the thin-walled cylindrical sleeve formed in the cylindrical shape, or are formed in an elongated shape in the circumferential direction or the axial direction of the thin-walled cylindrical sleeve formed in the cylindrical shape.

5. a shaft member that transmits rotational torque; a thin-walled cylindrical sleeve formed in a substantially cylindrical shape and into which the shaft member is press-fitted; a detection member disposed around the thin-walled cylindrical sleeve; a detection coil for detecting movement of the detection member in a circumferential direction around the shaft member; Equipped with The thin-walled cylindrical sleeve is formed by bending a thin plate into a cylindrical shape, and abutting portions of the thin plate in a circumferential direction of the cylindrical shape are welded with a plurality of welds, the thin-walled cylindrical sleeve has a tapered portion formed on an inner peripheral surface on a side where one end of the thin-walled cylindrical sleeve formed in the cylindrical shape in an axial direction is located, the tapered portion being formed so that the thickness becomes thinner as it approaches the end in the axial direction, Among the plurality of welds, an end weld, which is the weld located closest to the end, at least partially overlaps with the tapered portion in the axial direction, The end weld is a distance from the end to an outer surface of the end weld, which is a portion of the end weld located on the outer peripheral surface of the thin-walled cylindrical sleeve, is equal to or less than a distance L from the end to a tapered portion end, which is an end of the tapered portion opposite to the side where the end is located; A torque sensor in which the distance from the end to the inner surface of the end weld, which is the portion of the end weld located on the inner surface of the thin-walled cylindrical sleeve, is equal to or greater than the distance L.

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