Electric power steering device and method for manufacturing electric power steering device

Abstract

In order to suppress breakage of a permanent magnet used in a torque sensor, an electric power steering device 10 comprises: an input shaft 13 having an input shaft side hole part 13a inside; an output shaft 16 having an output shaft side hole part 16a inside; a torsion bar 17 having one end side arranged inside the input shaft side hole part 13a and the other end side arranged inside the output shaft side hole part 16a and connecting the input shaft 13 and the output shaft 16; and a torque sensor 30 having a permanent magnet 32 and having a magnet member 31 connected to an outer peripheral surface 13b of the input shaft 13. The input shaft 13 has a press-fitting part 14 for press-fitting the torsion bar 17 to the input shaft side hole part 13a, and the position of a connecting part 15 which is a part in the input shaft 13 to which the magnet member 31 is connected is different from the press-fitting part 14.

Description

Electric power steering device and method of manufacturing the same

[0001] The present disclosure relates to an electric power steering device and a method for manufacturing an electric power steering device.

[0002] An electric power steering device has a torque sensor that detects steering torque when the steering wheel is steered, and an electric motor that generates an assist force, and is able to assist the driver's steering force by generating an assist force using the electric motor based on the steering torque detected by the torque sensor. In such an electric power steering device, the input shaft and the output shaft are connected via a torsion bar, and the torque sensor detects a change in the relative rotation angle between the input shaft and the output shaft that accompanies slight twisting of the torsion bar when steering torque is transmitted from the input shaft to the output shaft via the torsion bar, thereby enabling detection of steering torque.

[0003] For example, in an electric power steering device described in Patent Document 1, the base end of a torsion bar is press-fitted and fixed to the input shaft, the tip of the torsion bar is fixed to the output shaft with a fixing pin, and a torque sensor unit is provided on the vehicle rear side of the output shaft. Also, in a steering device described in Patent Document 2, the torsion bar is fitted into a hole provided in the center of the input shaft and fixed to the input shaft with a pin, and the torsion bar is press-fitted into a hole provided in the center of the output shaft and fixed to the output shaft. Also, in the steering device described in Patent Document 2, the torque sensor has a magnet and a yoke, and the magnet is attached to the input shaft via a first sleeve and the yoke is attached to the output shaft via a second sleeve.

[0004] JP 2006-27350 A International Publication No. 2019 / 059230

[0005] Torque sensors used in electric power steering devices use permanent magnets, which are arranged on the input shaft or output shaft. However, because permanent magnets have low ductility, they may break when the shaft to which they are attached undergoes elastic deformation. For example, if a permanent magnet is attached directly or via a sleeve to the outer circumferential surface of the torsion bar press-fit portion of the input shaft, and the torsion bar is then press-fitted onto the input shaft, the input shaft may bulge slightly due to the press-fitting of the torsion bar, slightly increasing its diameter. In this case, the permanent magnet attached directly or via a sleeve to the outer circumferential surface of the input shaft may be unable to follow the bulge of the input shaft and may break. If the permanent magnet breaks, the torque sensor will no longer be able to detect steering torque. Therefore, electric power steering devices with torque sensors have room for improvement in terms of how permanent magnets are arranged.

[0006] The present disclosure has been made in consideration of the above, and aims to provide an electric power steering device that can suppress fracture of permanent magnets used in torque sensors, and a method for manufacturing an electric power steering device.

[0007] The electric power steering device of the present disclosure comprises an input shaft having an input shaft side hole portion on the inside, an output shaft having an output shaft side hole portion on the inside, a torsion bar having one end positioned inside the input shaft side hole portion and the other end positioned inside the output shaft side hole portion to connect the input shaft and the output shaft, and a torque sensor having a magnetic member having a permanent magnet and connected to the outer surface of the input shaft, wherein the input shaft has a press-fit portion into which the torsion bar is press-fitted into the input shaft side hole portion, and a connection portion on the input shaft where the magnetic member is connected is located at a different position in the axial direction of the input shaft from the press-fit portion.

[0008] With this configuration, the axial position of the connection portion on the input shaft to which the magnet member is connected is different from the position of the press-fit portion. Therefore, even if the diameter of the input shaft increases slightly at the position of the press-fit portion when the torsion bar is press-fitted into the input shaft side hole, the magnet member having the permanent magnet can be attached to the input shaft without being affected by the increase in the diameter of the input shaft. Therefore, a permanent magnet with low ductility can be attached to the input shaft while avoiding the increase in the diameter of the input shaft that occurs when the torsion bar is press-fitted. As a result, fracture of the permanent magnet used in the torque sensor can be suppressed.

[0009] In a preferred embodiment, the magnet member has a magnet sleeve in which the permanent magnet is disposed, and the magnet sleeve is connected to the connecting portion of the input shaft.

[0010] With this configuration, because the magnet sleeve in which the permanent magnet is disposed is connected to the connecting portion of the input shaft, the force acting on the permanent magnet when the magnet member is disposed on the input shaft can be minimized. In other words, the stress generated in the permanent magnet when the magnet member is disposed on the input shaft can be minimized. As a result, fracture of the permanent magnet used in the torque sensor can be suppressed.

[0011] In a preferred embodiment, the permanent magnet of the magnet member is connected to the connection portion of the input shaft.

[0012] According to this configuration, the permanent magnet of the magnet member is directly connected to the connecting portion of the input shaft, which reduces the number of parts and, as a result, reduces manufacturing costs.

[0013] In a preferred embodiment, the magnet member has a separation portion that extends from the position of the connection portion in the axial direction toward the side where the press-fit portion is located and is spaced apart from the outer peripheral surface of the input shaft, and at least a portion of the press-fit portion is located inside the separation portion in the radial direction of the input shaft.

[0014] With this configuration, at least a portion of the press-fit portion of the input shaft is located inside the separation portion of the magnet member, so the connection portion of the input shaft to which the magnet member is connected and the press-fit portion are positioned differently in the axial direction, and the depth of the input shaft side hole into which the torsion bar is press-fitted can be made shallow. This simplifies the cutting process used to form the input shaft side hole, and allows the permanent magnet of the magnet member to be attached to the input shaft while avoiding an increase in the diameter of the input shaft due to the press-fitting of the torsion bar. As a result, it is possible to reduce manufacturing costs and prevent breakage of the permanent magnets used in the torque sensor.

[0015] In a preferred embodiment, the press-fit portion is located closer to the output shaft in the axial direction than the connecting portion.

[0016] According to this configuration, the press-fit portion of the input shaft into which the torsion bar is press-fitted is located axially closer to the output shaft than the connection portion of the input shaft that connects the magnet member. This allows the depth of the input shaft side hole from the end of the input shaft to be shallower. This reduces the cutting area required to form the input shaft side hole by cutting the input shaft, simplifying the cutting process. Furthermore, by reducing the depth of the input shaft side hole from the end of the input shaft, the distance the torsion bar is pressed into the input shaft side hole when press-fitting the torsion bar into the input shaft side hole can be shortened. This improves assembly efficiency when assembling the torsion bar to the input shaft, thereby increasing workability during the assembly process. As a result, manufacturing costs can be reduced.

[0017] In a preferred embodiment, a torsion bar sleeve is disposed in the output shaft side hole between the output shaft side hole and the torsion bar disposed inside the output shaft side hole.

[0018] According to this configuration, since the torsion bar sleeve is disposed in the output-shaft-side hole portion of the output shaft, the torsion bar can be supported by the torsion bar sleeve within the output-shaft-side hole portion. This makes it possible to prevent the torsion bar from collapsing within the output-shaft-side hole portion. For example, when the torsion bar is press-fitted into the input-shaft-side hole portion of the input shaft with the torsion bar disposed in the output-shaft-side hole portion, by supporting the torsion bar with the torsion bar sleeve, the torsion bar can be press-fitted into the input-shaft-side hole portion while preventing the torsion bar from collapsing within the output-shaft-side hole portion. As a result, the assembly of the electric power steering device can be improved.

[0019] In a preferred embodiment, the transmission includes a housing in which the input shaft and the output shaft are disposed, and a bearing that supports the output shaft rotatably relative to the housing, with at least a portion of the bearing being disposed at the same position as the torsion bar sleeve in the axial direction.

[0020] According to this configuration, the bearing that rotatably supports the output shaft is positioned at least partially at the same axial position as the torsion bar sleeve, so that the load acting from the torsion bar on the torsion bar sleeve can be borne by the bearing, which is positioned a short distance from the torsion bar sleeve. This reduces the load acting on the bearing and prevents a large radial load from acting on the bearing, which would make it difficult to rotate the inner and outer rings of the bearing relative to each other. This prevents an increase in rotational resistance when rotating the output shaft supported by the bearing, and reduces rotational resistance when rotating the steering shaft having the output shaft. As a result, the steering torque when steering by rotating the steering wheel can be reduced, improving the operability of the electric power steering device.

[0021] In a preferred embodiment, a key lock collar of a locking device that restricts rotation of the input shaft is disposed on the outer peripheral surface of the input shaft, and the key lock collar is disposed at a position in the axial direction different from the press-fit portion.

[0022] With this configuration, the key lock collar is positioned at a different axial position from the press-fit portion, preventing the press-fit portion of the key lock collar and the input shaft from being axially positioned at the same position as the press-fit portion of the torsion bar on the input shaft. This prevents the mating force of the key lock collar with respect to the input shaft from varying from the mating force set at the time of design, which would occur if the diameter of the input shaft were to increase slightly at the press-fit portion when the torsion bar is press-fitted into the input shaft side hole. This prevents the slip torque, which is the torque that causes the key lock collar to rotate relative to the input shaft when a force that rotates the input shaft and the key lock collar relative to each other is applied to the key lock collar, from varying from the set slip torque. This prevents the key lock collar from rotating relative to the input shaft due to an unexpectedly small torque, ensuring proper mating of the key lock collar with the input shaft. As a result, the locking device having the key lock collar can be operated properly.

[0023] In a preferred embodiment, a connecting pin is disposed on the output shaft, connecting the torsion bar disposed inside the output shaft side hole portion to the output shaft.

[0024] With this configuration, the torsion bar is not press-fitted into the output shaft but is connected by a connecting pin, so the axial force applied to the torsion bar when the torsion bar is inserted into the output shaft hole and connected to the output shaft can be reduced. This prevents the torsion bar from buckling, which would occur if a large axial force were applied to the torsion bar from a position away from the press-fit portion of the torsion bar on the output shaft. This improves the ease of assembly when assembling the torsion bar to the output shaft, and increases the workability of the assembly process. As a result, manufacturing costs can be reduced.

[0025] The manufacturing method for an electric power steering device of the present disclosure includes an input shaft having an input shaft side hole portion on the inside, an output shaft having an output shaft side hole portion on the inside, a torsion bar with one end positioned inside the input shaft side hole portion and the other end positioned inside the output shaft side hole portion to connect the input shaft and the output shaft, and a torque sensor having a magnetic member connected to the outer peripheral surface of the input shaft, wherein the input shaft has a press-fit portion into which the torsion bar is press-fitted into the input shaft side hole portion, in the manufacturing method for an electric power steering device, the press-fit portion of the input shaft is formed by forging, and a connection portion which connects the magnetic member on the input shaft is positioned in the axial direction of the input shaft different from the position of the press-fit portion.

[0026] According to this configuration, the press-fit portion of the input shaft is formed by forging, thereby increasing the rigidity of the press-fit portion. Therefore, the connection between the input shaft and the torsion bar, which are connected by press-fitting the torsion bar into the input shaft-side hole of the input shaft, can be strengthened, and relative rotation between the input shaft and the torsion bar can be suppressed when steering torque is applied to the input shaft. This allows steering torque applied to the input shaft to be appropriately transmitted to the output shaft via the torsion bar, and allows the input shaft and the output shaft to rotate relative to each other through slight torsion of the torsion bar corresponding to the magnitude of the steering torque. Therefore, the magnitude of the steering torque can be detected by detecting the relative rotation between the input shaft and the output shaft with a torque sensor. As a result, the magnitude of the steering torque input to the input shaft can be appropriately detected.

[0027] The electric power steering device and the manufacturing method for the electric power steering device according to the present disclosure have the advantage of being able to suppress fracture of the permanent magnet used in the torque sensor.

[0028] FIG. 1 is a schematic diagram of an electric power steering device according to a first embodiment. FIG. 2 is a cross-sectional view of a main part of the electric power steering device according to the first embodiment. FIG. 3 is a schematic diagram illustrating an overview of a permanent magnet, a stator, and a magnetic flux collecting yoke that a torque sensor has. FIG. 4 is a cross-sectional view of a main part of an electric power steering device according to a second embodiment. FIG. 5 is a detailed view of part A in FIG. 4. FIG. 6 is a cross-sectional view of a main part of an electric power steering device according to a modified example of the second embodiment, showing a case in which the magnet member does not have a magnet sleeve.

[0029] 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.

[0030] [First Embodiment] Fig. 1 is a schematic diagram of an electric power steering device 10 according to a first embodiment. As shown in Fig. 1, the electric power steering device 10 includes, in the order in which a force applied by an operator is transmitted, a steering wheel 11, a steering shaft 12, a torque sensor 30, an electric motor 91, a reduction gear 92, a universal joint 81, an intermediate shaft 82, and a universal joint 83, which are joined to a stub shaft 84. In the following description, the direction along the central axis AX of the steering shaft 12 will be referred to as the "axial direction," and the direction intersecting (orthogonal to) the axial direction will be referred to as the "radial direction."

[0031] The steering wheel 11 is attached to one end of the steering shaft 12, and an intermediate shaft 82 is connected to the other end of the steering shaft 12 via a universal joint 81. The steering shaft 12 rotates due to torque input from the steering wheel 11. The steering shaft 12 includes an input shaft 13, an output shaft 16, and a torsion bar 17 (see FIG. 2). The torsion bar 17 is connected to both the input shaft 13 and the output shaft 16, and the input shaft 13 and the output shaft 16 are connected to each other via the torsion bar 17. The steering wheel 11 is attached to the steering shaft 12 by being connected to one end of the input shaft 13, and the torsion bar 17 extends from the other end of the input shaft 13 toward the side where the output shaft 16 is located. The torsion bar 17 extends from one end of the output shaft 16, and the other end of the output shaft 16 is connected to the intermediate shaft 82 via the universal joint 81. Rotational torque is transmitted between the input shaft 13 and the output shaft 16 via a torsion bar 17 connected to both.

[0032] A universal joint 81 and a universal joint 83 are disposed on both ends of the intermediate shaft 82 in the extending direction. One end of the intermediate shaft 82 is connected to the universal joint 81, and the other end is connected to the universal joint 83. Of the universal joints 81 and 83, the universal joint 81 connects the intermediate shaft 82 to the steering shaft 12. The universal joint 83 connects the intermediate shaft 82 to a stub shaft 84. One end of the stub shaft 84 is connected to the universal joint 83, and the other end is connected to a steering gear 85. The intermediate shaft 82 has one end connected to the steering shaft 12 and the other end connected to the stub shaft 84 via the universal joints 81 and 83. The universal joints 81 and 83 are, for example, Cardan joints. Rotation of the steering shaft 12 is transmitted to the stub shaft 84 via the intermediate shaft 82. Therefore, the intermediate shaft 82 can rotate together with the steering shaft 12.

[0033] The steering gear 85 includes a pinion gear 85a and a rack bar 85b. The pinion gear 85a is connected to the stub shaft 84. The rack bar 85b meshes with the pinion gear 85a. The steering gear 85 converts the rotational motion transmitted to the pinion gear 85a into linear motion by the rack bar 85b. The rack bar 85b is connected to a tie rod 86. The angle of the wheels changes as the rack bar 85b moves. In other words, the electric power steering device 10 is a rack-and-pinion type electric power steering device.

[0034] The electric power steering device 10 further includes an ECU (Electronic Control Unit) 90 and a vehicle speed sensor 95. The electric motor 91, the vehicle speed sensor 95, and the torque sensor 30 are electrically connected to the ECU 90. The reduction gear 92 is attached to the electric motor 91. The torque sensor 30 outputs the steering torque transmitted to the input shaft 13 to the ECU 90 via CAN (Controller Area Network) communication. The vehicle speed sensor 95 detects the traveling speed (vehicle speed) of the vehicle body on which the electric power steering device 10 is mounted. The vehicle speed sensor 95 is provided on the vehicle body and outputs the vehicle speed to the ECU 90 via CAN communication.

[0035] The ECU 90 controls the operation of the electric motor 91. The ECU 90 acquires signals from the torque sensor 30 and the vehicle speed sensor 95. When an ignition switch 98 is on, the ECU 90 is supplied with power from a power supply device 99 (e.g., an on-board battery). The ECU 90 calculates an auxiliary steering command value based on the steering torque and the vehicle speed. The ECU 90 adjusts the amount of power supplied to the electric motor 91 based on the auxiliary steering command value. The ECU 90 acquires information on the induced voltage of the electric motor 91 or information output from a resolver or the like provided in the electric motor 91. By the ECU 90 controlling the electric motor 91, the force required to operate the steering wheel 11 is reduced.

[0036] Next, the main parts of the electric power steering device 10 will be described in detail. Fig. 2 is a cross-sectional view of the main parts of the electric power steering device 10 according to the first embodiment. As shown in Fig. 2, the electric power steering device 10 includes an input shaft 13 which is a first shaft, an output shaft 16 which is a second shaft, a torsion bar 17, a torque sensor 30, a housing 20, and bearings 60 and 65. The input shaft 13, the output shaft 16, and the torsion bar 17 share a common center axis AX. The input shaft 13 and the output shaft 16 are connected in the axial direction, and the torsion bar 17 is disposed inside the input shaft 13 and the output shaft 16.

[0037] The input shaft 13 is, for example, a solid shaft. The input shaft 13 is rotatable around a central axis AX. A splined shaft portion (not shown) is formed on the end of the input shaft 13 opposite to the end connected to the output shaft 16, and the steering wheel 11 (see FIG. 1) is connected to the splined shaft portion directly or via another shaft. The input shaft 13 has, on its radially inner side, an input shaft side hole portion 13a that is a hole extending in the axial direction from the end connected to the output shaft 16.

[0038] The output shaft 16 is a cylindrical member having an output-shaft-side hole 16a and a connecting hole 16b extending axially on its radially inner side. The output shaft 16 is located relative to the input shaft 13 on the side where the end of the input shaft 13 where the input-shaft-side hole 13a is formed is located. The output shaft 16 is rotatable around the center axis AX. The connecting hole 16b has a larger inner diameter than the output-shaft-side hole 16a and is formed to a predetermined depth from the end of the output shaft 16 on the side where the input shaft 13 is connected to the opposite side from the side where the input shaft 13 is located. The output-shaft-side hole 16a extends from the end of the connecting hole 16b on the output shaft 16 toward the side opposite the side where the input shaft 13 is located. A portion of the input shaft 13 near its end is inserted into the connecting hole 16b.

[0039] The driving force generated by the electric motor 91 (see FIG. 1) is transmitted to the output shaft 16 via a worm (not shown) and a worm wheel 94 of the reduction gear device 92. That is, the driving force generated by the electric motor 91 is transmitted to the worm wheel 94 via the worm, causing the worm wheel 94 to rotate. The worm and the worm wheel 94 reduce the rotational speed of the driving force generated by the electric motor 91 and increase the torque.

[0040] The worm wheel 94 has a core metal portion 94a and a wheel tooth portion 94b. The core metal portion 94a is made of, for example, a metal material and is formed in a substantially annular shape. The wheel tooth portion 94b is made of, for example, a resin material and is integral with the core metal portion 94a and disposed on the outer periphery of the core metal portion 94a. The worm wheel 94 is fixed to the output shaft 16 by press-fitting the core metal portion 94a into the output shaft 16. The worm is directly or indirectly connected to the output shaft of the electric motor 91 and rotates integrally with the output shaft of the electric motor 91. The worm, which rotates due to the driving force generated by the electric motor 91, meshes with the wheel tooth portion 94b of the worm wheel 94. Therefore, the reduction gear 92 amplifies the driving force generated by the electric motor 91 and transmits it to the output shaft 16, thereby applying auxiliary steering torque to the output shaft 16. That is, the electric power steering device 10 according to the first embodiment is a column assist type electric power steering device in which an auxiliary steering torque is applied to the steering shaft 12 .

[0041] The torsion bar 17 is a solid elastic member extending in the axial direction. One axial end of the torsion bar 17 is disposed inside the input-shaft-side hole 13a of the input shaft 13, and the other axial end is disposed inside the output-shaft-side hole 16a of the output shaft 16, connecting the input shaft 13 and the output shaft 16. The portion of the torsion bar 17 that is disposed inside the input-shaft-side hole 13a of the input shaft 13 has a portion near its end press-fit into the input-shaft-side hole 13a. This allows the torsion bar 17 to be fixed to the input shaft 13 while allowing it to rotate relative to the input shaft 13.

[0042] More specifically, the torsion bar 17 has an expanded diameter portion 17a formed near the end of the torsion bar 17 that is disposed inside the input shaft side hole 13a of the input shaft 13. The expanded diameter portion 17a is disposed within a predetermined axial range from the end of the torsion bar 17 that is disposed inside the input shaft side hole 13a, and has a diameter slightly larger than the inner diameter of the input shaft side hole 13a. The expanded diameter portion 17a has a larger diameter than the rest of the torsion bar 17 other than the expanded diameter portion 17a, and the rest of the torsion bar 17 other than the expanded diameter portion 17a has a smaller diameter than the inner diameter of the input shaft side hole 13a. The expanded diameter portion 17a is press-fitted into the input shaft side hole 13a of the input shaft 13, thereby fixing the torsion bar 17 in the input shaft side hole 13a.

[0043] Since the torsion bar 17 is press-fitted into the input shaft 13 in this manner, the input shaft 13 has a press-fit portion 14, which is a portion into which the torsion bar 17 is press-fitted into the input shaft side hole 13a. The press-fit portion 14 of the input shaft 13 is a range in the axial direction where the expanded diameter portion 17a is located when the torsion bar 17 is press-fitted into the input shaft side hole 13a. In other words, the press-fit portion 14 is a range in the axial direction of the portion into which the expanded diameter portion 17a of the torsion bar 17 is press-fitted in the input shaft side hole 13a into which the torsion bar 17 is press-fitted.

[0044] The portion of the torsion bar 17 that is disposed inside the output-shaft-side hole 16a of the output shaft 16 is connected to the output shaft 16 by a connecting pin 70. In other words, the output shaft 16 is provided with a connecting pin 70 that connects the torsion bar 17, which is disposed inside the output-shaft-side hole 16a, to the output shaft 16.

[0045] More specifically, a through hole is formed radially through the end of the torsion bar 17 that is inserted into the output-shaft-side hole 16a of the output shaft 16. The torsion bar 17 also has an expanded-diameter portion 17b formed near the end that is disposed inside the output-shaft-side hole 16a of the output shaft 16, and the through hole is formed in the expanded-diameter portion 17b. A through hole is also formed radially through the output shaft 16 at the axial position where the through hole of the torsion bar 17 is formed. The through hole formed in the expanded-diameter portion 17b of the torsion bar 17 and the through hole formed in the output shaft 16 communicate with each other. A connecting pin 70 is inserted into the through hole formed in the torsion bar 17 and the through hole formed in the output shaft 16. As a result, the end of the torsion bar 17 that is inserted into the output-shaft-side hole 16a of the output shaft 16 is fixed to the output shaft 16 via the connecting pin 70.

[0046] A torsion bar sleeve 71 is disposed in the output-shaft-side hole 16a of the output shaft 16, between the output-shaft-side hole 16a and the torsion bar 17 disposed inside the output-shaft-side hole 16a. The torsion bar sleeve 71 is formed in a substantially cylindrical shape and is disposed inside the output-shaft-side hole 16a, at a position closer to the end on the side where the input shaft 13 is located in the axial direction. The torsion bar sleeve 71 has an outer diameter that is approximately the same as the inner diameter of the portion of the output-shaft-side hole 16a where the torsion bar sleeve 71 is disposed, and the inner diameter is slightly larger than the outer diameter of the portion of the torsion bar 17 located inside the torsion bar sleeve 71. The inner diameter of the torsion bar sleeve 71 is larger than the outer diameter of any portion of the torsion bar 17 from the portion located inside the torsion bar sleeve 71 to the end side where the expanded diameter portion 17b, through which the connecting pin 70 passes, is located.

[0047] The torsion bar sleeve 71 formed in this manner is fitted into the output shaft side hole 16a inside the output shaft side hole 16a, and the torsion bar 17 is disposed inside the output shaft side hole 16a passing through the inside of the torsion bar sleeve 71. The radial gap between the torsion bar sleeve 71 and the part of the torsion bar 17 located inside the torsion bar sleeve 71 is smaller than the gap between the torsion bar 17 located between the part where the torsion bar sleeve 71 is disposed and the expanded diameter part 17b through which the connecting pin 70 passes and the output shaft side hole 16a.

[0048] At least a portion of the steering shaft 12 is disposed inside the housing 20. The housing 20 houses the steering shaft 12 and the torque sensor 30, and the input shaft 13 and the output shaft 16 are disposed inside the housing 20. The housing 20 has a first housing 21 and a second housing 25. The first housing 21 is located closer to the input shaft 13 in the axial direction, and the second housing 25 is located closer to the output shaft 16 in the axial direction. The first housing 21 and the second housing 25 are connected in the axial direction by a connecting bolt 28. The second housing 25 has a space inside for arranging a worm (not shown) and a worm wheel 94, and the second housing 25 also functions as a gear box.

[0049] Bearings 60 and 65 are interposed between the housing 20 and the steering shaft 12, and the steering shaft 12 is rotatably supported by the bearings 60 and 65. The bearing 60 is provided as a first bearing that rotatably supports the output shaft 16 relative to the first housing 21. The bearing 65 is provided as a second bearing that rotatably supports the output shaft 16 relative to the second housing 25.

[0050] The bearing 60 and the bearing 65 are disposed on both axial sides of a position on the output shaft 16 where the worm wheel 94 is fixed. The bearing 60 is disposed on the axial side of the position on the output shaft 16 where the core metal portion 94a of the worm wheel 94 is fixed, on the side where the input shaft 13 is located, and the bearing 65 is disposed on the axial side opposite the side where the input shaft 13 is located, on the side where the core metal portion 94a of the worm wheel 94 is fixed. In other words, the bearing 65 is disposed on the axial side opposite the side where the bearing 60 is located, on the worm wheel 94.

[0051] More specifically, the output shaft 16 has a radial protrusion 16c that protrudes radially outward from a portion of the output shaft 16 where the bearings 60 and 65 are disposed. The axial width of the radial protrusion 16c is approximately the same as the axial width of a portion of the core metal portion 94a of the worm wheel 94 that is fixed to the output shaft 16, and is slightly larger than the width of the core metal portion 94a. The worm wheel 94 is fixed to the radial protrusion 16c on the output shaft 16 by press-fitting the core metal portion 94a into the radial protrusion 16c.

[0052] The bearing 60 and the bearing 65 are disposed on opposite sides of the radial protrusion 16c in the axial direction, so that the bearing 60 and the bearing 65 are disposed on opposite sides of the worm wheel 94 in the axial direction.

[0053] The torque sensor 30 includes a permanent magnet 32, a stator 40, a magnetic flux collecting yoke 50 (see FIG. 3), and a Hall IC 55 (see FIG. 3). Of these, the permanent magnet 32 ​​and the stator 40 are fixed to the steering shaft 12, and the magnetic flux collecting yoke 50 and the Hall IC 55 are fixed to the housing 20.

[0054] 3 is a schematic diagram illustrating an overview of the permanent magnet 32, stator 40, and magnetic flux collecting yoke 50 of the torque sensor 30. One of the permanent magnet 32 ​​and stator 40 of the torque sensor 30 is attached to a first shaft, and the other is attached to a second shaft. In the first embodiment, the permanent magnet 32 ​​is attached to the input shaft 13, which is the first shaft, and the stator 40 is attached to the output shaft 16, which is the second shaft. Of these, the permanent magnet 32 ​​is formed in a substantially cylindrical shape and is a multi-pole magnet in which a plurality of north poles and south poles are arranged alternately in the circumferential direction.

[0055] The stator 40 has a flange portion 41 and teeth portions 42. The flange portion 41 is formed in an annular plate shape with its thickness direction being the axial direction. The teeth portions 42 extend from the inner periphery of the annular flange portion 41 toward the axial direction of the flange portion 41 and are formed in a plate shape with their thickness direction being oriented in the radial direction of the flange portion 41. Furthermore, multiple teeth portions 42 are arranged side by side at intervals in the circumferential direction of the flange portion 41.

[0056] The stator 40 thus formed includes a pair of stators 40, a first stator 40a and a second stator 40b, each having an identical shape. The first stator 40a and the second stator 40b each have a flange portion 41 and teeth 42. That is, the first stator 40a has an annular first flange portion 41a and a plurality of first teeth 42a, and the second stator 40b has an annular second flange portion 41b and a plurality of second teeth 42b. The first stator 40a and the second stator 40b are both attached to the same shaft with their flange portions 41 positioned coaxially and oriented in a direction away from the other stator 40; in the first embodiment, both are attached to the output shaft 16.

[0057] That is, the first stator 40a is disposed with the first teeth 42a extending from the first flange 41a toward the second stator 40b, and the second stator 40b is disposed with the second teeth 42b extending from the second flange 41b toward the first stator 40a. In this case, since multiple first teeth 42a and multiple second teeth 42b are provided at intervals on the first flange 41a and the second flange 41b, the first stator 40a and the second stator 40b are combined such that the teeth 42 of one stator 40 are located in portions of the circumferential direction where the teeth 42 of the other stator 40 are not located.

[0058] The permanent magnet 32 ​​attached to the input shaft 13 is disposed radially inside the first stator 40 a and second stator 40 b combined in this manner. The permanent magnet 32 ​​and the stator 40 are also disposed with their axial directions aligned with the axial directions of the input shaft 13 and the output shaft 16. Therefore, the permanent magnet 32 ​​and the stator 40 are attached to the input shaft 13 and the output shaft 16 with the outer peripheral surface of the permanent magnet 32 ​​facing the teeth 42 of the stator 40. Because the permanent magnet 32 ​​and the stator 40 are disposed in this positional relationship, when torque is transmitted between the input shaft 13 and the output shaft 16 via the torsion bar 17 and the input shaft 13 and the output shaft 16 rotate slightly relative to each other, the relative positional relationship between the permanent magnet 32 ​​and the stator 40 changes, and the magnetic flux acting on the stator 40 from the permanent magnet 32 ​​changes accordingly.

[0059] Further, a magnetic flux collecting yoke 50 of the torque sensor 30 is disposed near the stator 40. The magnetic flux collecting yoke 50 is a component for detecting changes in the magnetic flux acting on the stator 40 from the permanent magnet 32, and is disposed near a flange portion 41 of the stator 40. Since the stator 40 is provided as a pair of a first stator 40a and a second stator 40b, the magnetic flux collecting yoke 50 is also provided as a pair of a first magnetic flux collecting yoke 50a and a second magnetic flux collecting yoke 50b corresponding to the first stator 40a and the second magnetic flux collecting yoke 50b. That is, the first magnetic flux collecting yoke 50a is disposed near the first flange portion 41a of the first stator 40a, and the second magnetic flux collecting yoke 50b is disposed near the second flange portion 41b of the second stator 40b.

[0060] The pair of magnetic flux collecting yokes 50 are located between two flange portions 41 of the stator 40 and overlap the flange portions 41 of the stator 40 with a gap in the axial direction. That is, the first magnetic flux collecting yoke 50a is located near the surface of the first flange portion 41a of the first stator 40a where the second flange portion 41b is located, and the second magnetic flux collecting yoke 50b is located near the surface of the second flange portion 41b of the second stator 40b where the first flange portion 41a is located. In this way, by positioning the magnetic flux collecting yokes 50 near the flange portions 41, the magnetic flux collecting yokes 50 can detect changes in the magnetic flux acting on the stator 40 from the permanent magnet 32 ​​when the input shaft 13 and the output shaft 16 rotate slightly relative to each other.

[0061] Furthermore, a Hall IC 55 is disposed between the two magnetic flux collecting yokes 50. The Hall IC 55 is disposed between the magnetic flux collecting yokes 50 at a position away from the portion of the magnetic flux collecting yoke 50 located near the flange portion 41 of the stator 40. The Hall IC 55 is capable of detecting changes in the magnetic flux density acting on the two magnetic flux collecting yokes 50, converting the detected changes in the magnetic flux density into an electric signal, and outputting the electric signal. Note that a magnetic sensor utilizing the magnetoresistance effect or the tunnel magnetoresistance effect can be used instead of the Hall IC. In short, it is sufficient if the change in the magnetic flux density occurring between the magnetic flux collecting yokes 50 can be output as an electric signal.

[0062] The magnetism collecting yoke 50 and the Hall IC 55 are attached to the housing 20. The magnetism collecting yoke 50 and the Hall IC 55 are fixed to, for example, a housing (not shown) that holds them, and the housing is attached to the first housing 21 in a state in which the magnetism collecting yoke 50 and the Hall IC 55 are disposed inside the first housing 21. As a result, the magnetism collecting yoke 50 is disposed inside the first housing 21 in a state in which the pair of magnetism collecting yokes 50 are positioned between two flange portions 41 of the stator 40, and the Hall IC 55 is disposed between the two magnetism collecting yokes 50.

[0063] The permanent magnet 32 ​​of the torque sensor 30 is attached to the input shaft 13 by a magnet sleeve 33. The permanent magnet 32 ​​and the magnet sleeve 33 constitute a magnet member 31 of the torque sensor 30, and the permanent magnet 32 ​​is attached to the input shaft 13 by connecting the magnet member 31 to the outer circumferential surface 13b of the input shaft 13. Of the permanent magnet 32 ​​and the magnet sleeve 33 of the magnet member 31, the magnet sleeve 33 is a cylindrical member, and is attached to the input shaft 13 by press-fitting the input shaft 13 into the magnet sleeve 33. The permanent magnet 32 ​​is disposed on the outer circumferential surface of the magnet sleeve 33, and is fixed to the magnet sleeve 33 by, for example, an adhesive.

[0064] The magnet member 31 having the permanent magnet 32 ​​is attached to the input shaft 13 by press-fitting the input shaft 13 into the magnet sleeve 33 in this manner. Therefore, at the connection portion 15, which is the portion of the input shaft 13 where the magnet member 31 is connected, the magnet sleeve 33 of the magnet member 31 is connected to the input shaft 13. The connection portion 15 is the portion on the outer circumferential surface 13b of the input shaft 13 where the magnet member 31 is attached by being connected. The magnet member 31 is connected and attached to the connection portion 15 of the input shaft 13, for example, by press-fitting. The permanent magnet 32 ​​is rotatable integrally with the input shaft 13 by attaching the magnet member 31 having the permanent magnet 32 ​​to the input shaft 13.

[0065] Furthermore, the magnet member 31 attached to the input shaft 13 has a separation portion 34 that is separated from the outer peripheral surface 13b of the input shaft 13. The separation portion 34 is located at a different axial position from the connection portion 15, and in the first embodiment, the separation portion 34 is located on the axial side of the connection portion 15 where the output shaft 16 is located. More specifically, in the first embodiment, the input shaft 13 has a larger outer diameter at the position of the connection portion 15 than at the portion of the magnet member 31 where the separation portion 34 is located. In other words, the outer diameter at the same axial position on the input shaft 13 as the portion where the separation portion 34 is located is smaller than the outer diameter at the position of the connection portion 15.

[0066] In contrast, the inner diameter of the magnet member 31 is the same at the position of the connecting portion 15 and the position of the separating portion 34. That is, the inner diameter of the magnet sleeve 33 of the magnet member 31 is the same at the position of the connecting portion 15 and the position of the separating portion 34. Therefore, the inner circumferential surface of the magnet member 31 at the position of the separating portion 34 is spaced radially outward from the outer circumferential surface 13b of the input shaft 13.

[0067] The connection portion 15 of the input shaft 13 to which the magnet member 31 is connected is positioned in a different axial position from the press-fit portion 14. When the magnet member 31 is attached to the input shaft 13 during manufacture of the electric power steering device 10, the connection portion 15, which is the portion of the input shaft 13 to which the magnet member 31 is connected, is attached so that the axial position of the connection portion 15 is different from the position of the press-fit portion 14. This allows the magnet member 31 having the permanent magnet 32 ​​to be attached to the input shaft 13 without being affected by the slight expansion of the diameter of the input shaft 13 at the position of the press-fit portion 14 caused by press-fitting the torsion bar 17 into the input shaft-side hole 13a of the input shaft 13.

[0068] In the first embodiment, the connection portion 15 of the input shaft 13 to which the magnet member 31 is connected is located on the side where the output shaft 16 is located relative to the position of the press-fit portion 14 in the axial direction. In other words, the press-fit portion 14 of the torsion bar 17 in the input shaft 13 is located on the opposite side of the side where the connection portion 15 is located on the output shaft 16 side in the axial direction.

[0069] The stator 40 is attached to the output shaft 16 by a stator sleeve 43 and a carrier 44. The stator sleeve 43 is a cylindrical member, and is attached to the output shaft 16 by press-fitting the output shaft 16 into the stator sleeve 43. The carrier 44 is a cylindrical member, and is formed integrally with the stator sleeve 43 by injection molding. Therefore, when the stator sleeve 43 is attached to the output shaft 16, the carrier 44 is also attached to the output shaft 16 together with the stator sleeve 43.

[0070] The carrier 44, which is attached to the output shaft 16 by the stator sleeve 43, is supported by the stator sleeve 43 and is disposed at a position facing the input shaft 13 from the output shaft 16, and is disposed at a radially outer position of the input shaft 13. Furthermore, the carrier 44 is disposed at the same axial position as the permanent magnet 32 ​​of the magnet member 31, and is disposed radially outward of the permanent magnet 32.

[0071] The stators 40 are attached to the carrier 44 arranged in this manner. More specifically, the first stator 40a and the second stator 40b are attached to the carrier 44 with the teeth 42 located radially inside the carrier 44 and the flanges 41 protruding from the radially inside to the radially outside of the carrier 44. As a result, the pair of stators 40, the first stator 40a and the second stator 40b, are both arranged in the same position as the permanent magnet 32 ​​in the axial direction, and are arranged radially outside the permanent magnet 32.

[0072] Furthermore, the first stator 40a and the second stator 40b are attached to a carrier 44 formed integrally with a stator sleeve 43 attached to the output shaft 16, and are therefore rotatable integrally with the output shaft 16. The stator 40 thus arranged to be rotatable integrally with the output shaft 16 has a flange portion 41 that protrudes outward in the radial direction of the output shaft 16, and is fixed to the output shaft 16.

[0073] As described above, the permanent magnet 32 ​​is fixed to the input shaft 13, and the stator 40 is fixed to the output shaft 16, so that the permanent magnet 32 ​​and the stator 40 are disposed inside the housing 20 together with the input shaft 13 and the output shaft 16. In the first embodiment, the permanent magnet 32 ​​and the stator 40 are disposed inside the first housing 21.

[0074] A key lock collar 75 included in a locking device (not shown) that restricts rotation of the steering shaft 12 is attached to the steering shaft 12. The key lock collar 75 is sleeve-shaped and is disposed on the outer peripheral surface 13b of the input shaft 13 near the portion of the input shaft 13 where the press-fit portion 14 is located in the axial direction. Therefore, the locking device that restricts rotation of the steering shaft 12 restricts rotation of the input shaft 13 included in the steering shaft 12. The input shaft 13 is press-fitted into the key lock collar 75, thereby preventing relative rotation of the key lock collar 75 with respect to the input shaft 13. For example, when the driver of the vehicle removes the key, a pin of the locking device protrudes from the housing 20 toward the key lock collar 75 and engages with the key lock collar 75. This fixes the housing 20 and the input shaft 13 so that they cannot rotate relative to each other, and the steering wheel 11 cannot be rotated with the key removed.

[0075] The bearings 60 and 65, which rotatably support the output shaft 16, are so-called rolling bearings. Of the bearings 60 and 65, the bearing 60 rotatably supports the output shaft 16 relative to the first housing 21. That is, the bearing 60 is disposed between the output shaft 16 and the first housing 21 by fitting its inner circumferential surface to the output shaft 16 and its outer circumferential surface to the first housing 21, and rotatably supports the output shaft 16 relative to the first housing 21. The inner circumferential surface 22 of the first housing 21, into which the bearing 60 is fitted, is formed with a step portion 23 that connects portions of the inner circumferential surface 22 that are different in size in the radial direction. The step portion 23 faces in the axial direction, and the bearing 60 abuts against the step portion 23 in the axial direction. As a result, the bearing 60 is fitted into the first housing 21 in a state in which relative axial movement of the bearing 60 with respect to the first housing 21 is restricted by the step portion 23.

[0076] Furthermore, at least a portion of the bearing 60 is disposed at the same position in the axial direction as the torsion bar sleeve 71. In other words, the bearing 60 is disposed radially outward of the torsion bar sleeve 71 with at least a portion of the bearing 60 in the same position as the torsion bar sleeve 71, and supports the output shaft 16 rotatably relative to the first housing 21.

[0077] On the other hand, the bearing 65 rotatably supports the output shaft 16 with respect to the second housing 25. That is, the bearing 65 is disposed between the output shaft 16 and the second housing 25 by fitting its inner circumferential surface onto the output shaft 16 and its outer circumferential surface into the second housing 25, and supports the output shaft 16 rotatably with respect to the second housing 25. A protrusion 27 that protrudes radially inward is formed on the inner circumferential surface 26 of the second housing 25 into which the bearing 65 is fitted, and the bearing 65 abuts against the protrusion 27 in the axial direction. As a result, the bearing 65 is fitted into the second housing 25 in a state where relative axial movement of the bearing 65 with respect to the second housing 25 is restricted by the protrusion 27.

[0078] Next, the operation of the electric power steering device 10 will be described. When the steering wheel 11 is operated while driving a vehicle equipped with the electric power steering device 10, the steering force applied to the steering wheel 11 is transmitted from the steering wheel 11 to the steering shaft 12. The steering force transmitted to the steering shaft 12 is transmitted as steering torque from the steering shaft 12 to the intermediate shaft 82, and from the intermediate shaft 82 to the pinion gear 85a via the stub shaft 84. As a result, the steering gear 85 having the pinion gear 85a converts the rotational motion transmitted from the pinion gear 85a into linear motion of the rack bar 85b, thereby operating the tie rod 86.

[0079] The electric power steering device 10 according to the first embodiment also includes an electric motor 91 that generates an auxiliary steering torque to assist the driver in steering. The electric motor 91 generates the auxiliary steering torque based on the steering torque detected by the torque sensor 30 that is disposed between the input shaft 13 and the output shaft 16 of the steering shaft 12.

[0080] The torque sensor 30 detects the steering torque applied from the steering wheel 11 to the steering shaft 12 based on the angle of relative rotation between the input shaft 13 and the output shaft 16. That is, since the input shaft 13 and the output shaft 16 are connected via the torsion bar 17, when a steering torque is applied to the input shaft 13 of the steering shaft 12, the steering torque is transmitted between the input shaft 13 and the output shaft 16 via the torsion bar 17.

[0081] In other words, the torsion bar 17 is press-fitted into the input-shaft-side hole 13a of the input shaft 13 at the press-fit portion 14, and the torsion bar 17 rotates integrally with the input shaft 13 at the position of the press-fit portion 14. Therefore, when the input shaft 13 rotates, steering torque is transmitted from the input shaft 13 to the torsion bar 17 at the position of the press-fit portion 14. Furthermore, the torsion bar 17 is connected to the output shaft 16 by a connecting pin 70 inside the output-shaft-side hole 16a, and the torsion bar 17 and the output shaft 16 rotate integrally at the position connected by the connecting pin 70. Therefore, when the torsion bar 17 rotates, steering torque is transmitted from the torsion bar 17 to the output shaft 16 at the position connected by the connecting pin 70.

[0082] As a result, when a steering torque is applied to the input shaft 13 of the steering shaft 12, the steering torque is transmitted from the input shaft 13 to the output shaft 16 via the torsion bar 17. At that time, the torsion bar 17 is slightly twisted, causing the input shaft 13 and the output shaft 16 to rotate relative to each other.

[0083] In the torque sensor 30, the magnet member 31 having the permanent magnet 32 ​​is attached to the input shaft 13, and the stator 40 is attached to the output shaft 16. When the input shaft 13 and the output shaft 16 rotate relative to each other, the permanent magnet 32 ​​and the stator 40 of the torque sensor 30 also rotate relative to each other. The angle of relative rotation between the permanent magnet 32 ​​and the stator 40 increases as the steering torque acting between the input shaft 13 and the output shaft 16 increases.

[0084] When the permanent magnet 32 ​​and the stator 40 rotate relative to each other, the magnetic flux acting from the permanent magnet 32 ​​on the stator 40 changes. The magnetic flux collecting yoke 50 arranged near the stator 40 is capable of detecting the change in the magnetic flux acting from the permanent magnet 32 ​​on the stator 40. Therefore, when the permanent magnet 32 ​​and the stator 40 rotate relative to each other in conjunction with the relative rotation of the input shaft 13 and the output shaft 16, the magnetic flux collecting yoke 50 arranged near the stator 40 can detect the change in the magnetic flux acting from the permanent magnet 32 ​​on the stator 40.

[0085] In this way, the magnetic flux acting on the stator 40 from the permanent magnet 32, which is detected by the magnetism collecting yoke 50, changes depending on the angle of relative rotation between the permanent magnet 32 ​​and the stator 40. The Hall IC 55 detects the magnetic flux, which changes depending on the angle of relative rotation between the permanent magnet 32 ​​and the stator 40 and is detected by the magnetism collecting yoke 50, using a Hall element, converts the detected magnetic flux into an electric signal using an output circuit, and transmits the signal to the ECU 90 as an output signal from the torque sensor 30. In other words, the torque sensor 30 detects the change in the magnetic flux acting on the stator 40 from the permanent magnet 32 ​​using the magnetism collecting yoke 50 and the Hall IC 55, thereby detecting the steering torque applied to the input shaft 13, and transmits the detected steering torque to the ECU 90 as an electric signal.

[0086] The ECU 90 operates the electric motor 91 based on the electrical signal transmitted from the torque sensor 30, causing the electric motor 91 to generate an assist steering torque. In other words, the electrical signal transmitted from the Hall IC 55 of the torque sensor 30 to the ECU 90 changes according to the angle of relative rotation between the permanent magnet 32 ​​and the stator 40, and changes based on the steering torque acting between the input shaft 13 and the output shaft 16. Therefore, the ECU 90 uses the electrical signal transmitted from the Hall IC 55 of the torque sensor 30 as information that changes depending on the steering torque acting on the input shaft 13 and the output shaft 16, and adjusts the value of the power supplied to the electric motor 91 based on the electrical signal transmitted from the Hall IC 55, causing the electric motor 91 to generate an assist steering torque.

[0087] That is, the ECU 90 acquires a steering torque signal from the torque sensor 30, acquires a vehicle speed signal from the vehicle speed sensor 95, and further acquires operation information of the electric motor 91 from a rotation detection device provided in the electric motor 91, and causes the electric motor 91 to generate an auxiliary steering torque based on this operation information, steering torque, and vehicle speed signal. The auxiliary steering torque generated by the electric motor 91 is transmitted to the output shaft 16 of the steering shaft 12 via a worm (not shown) and a worm wheel 94 connected to the output shaft of the electric motor 91. As a result, the steering force applied to the steering wheel 11 by the driver is assisted by the auxiliary steering torque generated by the electric motor 91.

[0088] As described above, in the electric power steering device 10 according to the first embodiment, the torsion bar 17 is press-fitted into the input shaft-side hole 13a of the input shaft 13 at the press-fit portion 14, and the magnet member 31 of the torque sensor 30 has a connection portion 15, to which the magnet member 31 is connected, in the axial direction, which is different from the position of the press-fit portion 14. As a result, even if the diameter of the input shaft 13 increases slightly at the press-fit portion 14 when the torsion bar 17 is press-fitted into the input shaft-side hole 13a of the input shaft 13, the magnet member 31 having the permanent magnet 32 ​​can be attached to the input shaft 13 without being affected by the increase in the diameter of the input shaft 13. Therefore, the permanent magnet 32, which has low ductility, can be attached to the input shaft 13 while avoiding the increase in the diameter of the input shaft 13 that occurs when the torsion bar 17 is press-fitted. As a result, fracture of the permanent magnet 32 ​​used in the torque sensor 30 can be suppressed.

[0089] Furthermore, the magnet member 31 has a magnet sleeve 33 in which the permanent magnet 32 ​​is disposed, and the magnet sleeve 33 is connected to the connection portion 15 of the input shaft 13, so that it is possible to minimize the force acting on the permanent magnet 32 ​​when the magnet member 31 is disposed on the input shaft 13. In other words, it is possible to minimize the stress generated in the permanent magnet 32 ​​when the magnet member 31 is disposed on the input shaft 13. As a result, it is possible to prevent the permanent magnet 32 ​​used in the torque sensor 30 from breaking.

[0090] Furthermore, since a torsion bar sleeve 71 is disposed in the output-shaft-side hole 16a of the output shaft 16 between the output-shaft-side hole 16a and the torsion bar 17, the torsion bar 17 can be supported by the torsion bar sleeve 71 in the output-shaft-side hole 16a. This makes it possible to prevent the torsion bar 17 from collapsing in the output-shaft-side hole 16a. For example, when the torsion bar 17 is press-fitted into the input-shaft-side hole 13a of the input shaft 13 with the torsion bar 17 disposed in the output-shaft-side hole 16a, by supporting the torsion bar 17 with the torsion bar sleeve 71, the torsion bar 17 can be press-fitted into the input-shaft-side hole 13a while preventing the torsion bar 17 from collapsing in the output-shaft-side hole 16a. As a result, the assembly of the electric power steering device 10 can be improved.

[0091] Furthermore, the bearing 60, which rotatably supports the output shaft 16 relative to the housing 20, is located at least partially at the same position in the axial direction as the torsion bar sleeve 71, so that the load acting from the torsion bar 17 on the torsion bar sleeve 71 can be efficiently borne by the bearing 60. In other words, the load acting from the torsion bar 17 on the torsion bar sleeve 71 can be borne by the bearing 60, which is located a short distance from the torsion bar sleeve 71. This reduces the load acting on the bearing 60 and prevents the inner ring and outer ring of the bearing 60 from becoming difficult to rotate relative to each other, which would be caused by a large radial load acting on the bearing 60. Therefore, it is possible to prevent an increase in rotational resistance when rotating the output shaft 16 supported by the bearing 60, and to reduce rotational resistance when rotating the steering shaft 12 having the output shaft 16. As a result, the steering torque when steering by rotating the steering wheel 11 can be reduced, and the operability of the electric power steering device 10 can be improved.

[0092] Furthermore, a connecting pin 70 is disposed on the output shaft 16, connecting the torsion bar 17 disposed inside the output-shaft-side hole 16a to the output shaft 16, thereby preventing buckling of the torsion bar 17. In other words, when the torsion bar 17 press-fitted onto the input shaft 13 is also press-fitted onto the output shaft 16, the axial force applied to the torsion bar 17 tends to be applied from a position distant from the portion of the torsion bar 17 press-fitted onto the output shaft 16. In this case, the torsion bar 17 is likely to buckle due to the increased distance in the axial direction between the portion where the force is applied and the press-fit portion.

[0093] In contrast, in the first embodiment, the torsion bar 17 and the output shaft 16 are connected by the connecting pin 70, so that the axial force applied to the torsion bar 17 can be reduced when the torsion bar 17 is inserted into the output-shaft-side hole 16a and connected to the output shaft 16. This prevents the torsion bar 17 from buckling, which would otherwise occur if a large axial force were applied to the torsion bar 17 from a position away from the portion of the torsion bar 17 that is press-fitted into the output shaft 16. This improves the ease of assembly when assembling the torsion bar 17 to the output shaft 16, thereby increasing the workability of the assembly process. As a result, manufacturing costs can be reduced.

[0094] Second Embodiment Next, an electric power steering device 10 according to a second embodiment will be described. Components that are the same as those in the first embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted. The following description will focus on differences from the first embodiment.

[0095] 4 is a cross-sectional view of a main portion of an electric power steering device 10 according to the second embodiment. In the electric power steering device 10 according to the second embodiment, as in the first embodiment, the torsion bar 17 is press-fitted into the input shaft-side hole 13a of the input shaft 13, and the connection portion 15, which is the portion of the input shaft 13 to which the magnet member 31 is connected, is positioned in a different axial direction of the input shaft 13 from the press-fit portion 14.

[0096] In the second embodiment, unlike the first embodiment, the connection portion 15 of the input shaft 13 to which the magnet member 31 is connected is located on the opposite side of the output shaft 16 from the position of the press-fit portion 14 in the axial direction. In other words, the press-fit portion 14 of the torsion bar 17 in the input shaft 13 is located closer to the output shaft 16 in the axial direction than the position of the connection portion 15. In more detail, the press-fit portion 14 is located near the position of the connection portion 15 in the axial direction, and does not have a portion whose position in the axial direction is the same as that of the connection portion 15, and is located slightly closer to the output shaft 16 than the position of the connection portion 15.

[0097] Furthermore, in the second embodiment, the magnet member 31 has a separation portion 34 that is separated from the outer peripheral surface 13b of the input shaft 13 and extends from the position of the connection portion 15 toward the side where the press-fit portion 14 is located in the axial direction of the input shaft 13. Therefore, at least a portion of the press-fit portion 14, which is located axially near the position of the connection portion 15, is located inside the separation portion 34 of the magnet member 31 in the radial direction of the input shaft 13. In other words, at least a portion of the press-fit portion 14 in the axial direction is located in the same position as the separation portion 34 of the magnet member 31 in the axial direction.

[0098] More specifically, the permanent magnet 32 ​​attached to the magnet sleeve 33 is disposed in the spaced apart portion 34 of the magnet member 31. Therefore, at least a portion of the press-fit portion 14 is located radially inside the permanent magnet 32 ​​disposed in the spaced apart portion 34 of the magnet member 31.

[0099] In the second embodiment, the input shaft side hole 13a formed in the input shaft 13 is formed substantially only in the press-fit portion 14, and the input shaft side hole 13a formed in the press-fit portion 14 opens to the end of the input shaft 13 on the output shaft 16 side. In other words, the press-fit portion 14 is formed from the end of the input shaft 13 on the output shaft 16 side toward the side opposite to the side where the output shaft 16 is located in the axial direction.

[0100] In this way, the press-fit portion 14 of the input shaft 13 located near the end of the input shaft 13 on the output shaft 16 side is formed by forging. That is, in the manufacturing method for the electric power steering device 10 according to the second embodiment, the range in the axial direction of the input shaft 13 where the press-fit portion 14 is to be formed is forged from the outer peripheral surface 13b side. The input shaft 13 has a forged press-fit portion 14. Furthermore, the input shaft side hole 13a is formed by cutting the press-fit portion 14 of the input shaft 13, which is forged from the outer peripheral surface 13b side, from the end of the input shaft 13 where the output shaft 16 is located. This improves the rigidity of the outer peripheral surface 13b side of the press-fit portion 14 of the input shaft 13, and the input shaft side hole 13a, into which the torsion bar 17 is press-fitted, is formed with high precision.

[0101] 5 is a detailed view of portion A in FIG. 4. The torsion bar 17 is press-fitted into the input-shaft-side hole 13a formed in the press-fit portion 14 of the input shaft 13. A pressed-in portion 17c is formed in the portion of the expanded-diameter portion 17a of the torsion bar 17 on the side where the output shaft 16 is located, which is press-fitted into the input-shaft-side hole 13a. The pressed-in portion 17c is formed such that the end of the expanded-diameter portion 17a on the side where the output shaft 16 is located forms a plane perpendicular to the axial direction of the input shaft 13, i.e., the axial direction of the torsion bar 17. In other words, the pressed-in portion 17c of the torsion bar 17 has a smaller diameter than the expanded-diameter portion 17a and forms a step with the portion connected to the expanded-diameter portion 17a, and this step is formed as a plane perpendicular to the axial direction of the torsion bar 17.

[0102] The push-in portion 17c of the torsion bar 17 formed in this manner is formed so that the axial position of the push-in portion 17c when the expanded diameter portion 17a is pressed into the input shaft side hole portion 13a of the input shaft 13 is approximately the same as the position of the end portion of the input shaft 13 on the output shaft 16 side.

[0103] In the second embodiment, a key lock collar 75 is also disposed on the outer peripheral surface 13b of the input shaft 13. The key lock collar 75 is disposed at a different axial position from the press-fit portion 14, and is disposed on the opposite axial side of the press-fit portion 14 from the side on which the output shaft 16 is located. In other words, the key lock collar 75 is disposed on the opposite axial side of the magnet member 31 disposed on the input shaft 13 from the side on which the output shaft 16 is located.

[0104] In the second embodiment, unlike the first embodiment, the key lock collar 75 is disposed on the outer peripheral surface 13b of the input shaft 13 via a slip ring 76. The slip ring 76 is a leaf spring formed in a substantially annular shape and is disposed between the inner peripheral surface of the key lock collar 75 and the outer peripheral surface 13b of the input shaft 13. The elastic force of the leaf spring generates frictional forces between the inner peripheral surface of the key lock collar 75 and the outer peripheral surface of the slip ring 76, and between the outer peripheral surface 13b of the input shaft 13 and the inner peripheral surface of the slip ring 76, thereby holding the key lock collar 75 on the outer peripheral surface 13b of the input shaft 13.

[0105] When a large force is input in a direction that rotates the key lock collar 75 and the input shaft 13 relative to each other, the slip ring 76 arranged in this manner slips, allowing the key lock collar 75 to rotate relative to the input shaft 13. Therefore, when a large force equal to or greater than a predetermined value is input in a direction that rotates the key lock collar 75 and the input shaft 13 relative to each other, the key lock collar 75 is arranged to be rotatable relative to the input shaft 13 due to slip of the slip ring 76.

[0106] As described above, in the electric power steering device 10 according to the second embodiment, similarly to the first embodiment, the axial position of the connection portion 15, which is the portion of the input shaft 13 to which the magnet member 31 of the torque sensor 30 is connected, is different from the position of the press-fit portion 14, into which the torsion bar 17 is press-fitted, on the input shaft 13. Therefore, the permanent magnet 32, which is included in the magnet member 31 and has low ductility, can be attached to the input shaft 13 while avoiding an increase in the diameter of the input shaft 13 due to the press-fitting of the torsion bar 17. As a result, fracture of the permanent magnet 32 ​​used in the torque sensor 30 can be suppressed.

[0107] Furthermore, the press-fit portion 14 of the input shaft 13, into which the torsion bar 17 is press-fitted, is located closer to the output shaft 16 in the axial direction of the input shaft 13 than the connection portion 15, which connects the magnet member 31 on the input shaft 13. This allows the depth of the input shaft side hole 13a from the end of the input shaft 13 to be shallower, and reduces the cutting area required when forming the input shaft side hole 13a by cutting the input shaft 13. This simplifies the cutting process when forming the input shaft side hole 13a.

[0108] Furthermore, by making the depth of the input shaft side hole 13a from the end of the input shaft 13 shallower, the distance by which the torsion bar 17 is pressed into the input shaft side hole 13a can be shortened when press-fitting the torsion bar 17 into the input shaft side hole 13a. This improves the ease of assembly when assembling the torsion bar 17 to the input shaft 13, and increases the workability in the assembly process. As a result, manufacturing costs can be reduced.

[0109] Furthermore, because the torsion bar 17 has the push-in portion 17c formed in the enlarged diameter portion 17a, when the torsion bar 17 is press-fitted into the input shaft-side hole 13a of the input shaft 13, the torsion bar 17 can be easily press-fitted into the input shaft-side hole 13a by applying a load to the push-in portion 17c. This prevents the torsion bar 17 from buckling due to the application of a load to a position on the torsion bar 17 away from the enlarged diameter portion 17a when press-fitting the torsion bar 17 into the input shaft-side hole 13a of the input shaft 13. This improves the ease of assembly when assembling the torsion bar 17 to the input shaft 13, thereby increasing the workability of the assembly process. As a result, manufacturing costs can be reduced.

[0110] Furthermore, at least a portion of the press-fit portion 14 of the input shaft 13 is located radially inward of the separation portion 34 of the magnet member 31, so the connection portion 15 to which the magnet member 31 is connected on the input shaft 13 and the press-fit portion 14 can be positioned differently in the axial direction, and the depth of the input shaft side hole 13a into which the torsion bar 17 is press-fitted can be made shallow. This simplifies the cutting process for forming the input shaft side hole 13a in the input shaft 13, and allows the permanent magnet 32 ​​of the magnet member 31 to be attached to the input shaft 13 while avoiding an increase in the diameter of the input shaft 13 due to the press-fitting of the torsion bar 17. As a result, breakage of the permanent magnet 32 ​​used in the torque sensor 30 can be suppressed while reducing manufacturing costs.

[0111] Furthermore, because the press-fit portion 14 of the input shaft 13 is formed by forging, the rigidity of the press-fit portion 14 can be increased. Therefore, by press-fitting the torsion bar 17 into the input-shaft-side hole 13a of the input shaft 13, the connection between the input shaft 13 and the torsion bar 17 can be strengthened, and relative rotation between the input shaft 13 and the torsion bar 17 can be suppressed when steering torque is applied to the input shaft 13. As a result, steering torque applied to the input shaft 13 can be appropriately transmitted to the output shaft 16 via the torsion bar 17, and the input shaft 13 and the output shaft 16 can be rotated relative to each other by a slight twist of the torsion bar 17 corresponding to the magnitude of the steering torque. Therefore, the magnitude of the steering torque can be detected by detecting the relative rotation between the input shaft 13 and the output shaft 16 with the torque sensor 30. As a result, the magnitude of the steering torque input to the steering shaft 12 can be appropriately detected.

[0112] Furthermore, the key lock collar 75 disposed on the outer peripheral surface 13b of the input shaft 13 is disposed at a position different from the press-fit portion 14 in the axial direction of the input shaft 13, thereby preventing the portion where the key lock collar 75 is disposed on the input shaft 13 via the slip ring 76 from being at the same axial position as the press-fit portion 14 of the torsion bar 17 on the input shaft 13. This prevents the fitting force of the key lock collar 75, applied via the slip ring 76 to the input shaft 13, from varying from the fitting force set at the time of design, which would be caused by the diameter of the input shaft 13 becoming slightly larger at the position of the press-fit portion 14 when the torsion bar 17 is press-fitted into the input shaft-side hole 13a of the input shaft 13. This prevents the slip torque, which is a torque that rotates the key lock collar 75 relative to the input shaft 13, from varying from the set slip torque when a force in a direction that rotates the input shaft 13 and the key lock collar 75 relative to each other is applied to the key lock collar 75 by a locking device (not shown). Therefore, it is possible to prevent the key lock collar 75 from rotating relative to the input shaft 13 due to an unexpectedly small torque, and to properly fit the key lock collar 75 to the input shaft 13. As a result, it is possible to properly operate a locking device having the key lock collar 75.

[0113] [Variations] In the first and second embodiments described above, the magnet member 31 connected to the input shaft 13 has the magnet sleeve 33, and the permanent magnet 32 ​​is arranged in the magnet sleeve 33, but the magnet member 31 does not necessarily have to have the magnet sleeve 33.

[0114] 6 is a cross-sectional view of a main portion of the electric power steering device 10, showing a modified example of the electric power steering device 10 according to the second embodiment, in which the magnet member 31 does not have the magnet sleeve 33. The magnet member 31 may be formed solely of a permanent magnet 35 without having the magnet sleeve 33. In other words, the permanent magnet 35 of the magnet member 31 may be directly connected to the connection portion 15 of the input shaft 13 without the magnet sleeve 33. The permanent magnet 35 directly connected to the connection portion 15 of the input shaft 13 is a multi-pole magnet that is formed in a substantially cylindrical shape and has a plurality of north and south poles alternately arranged in the circumferential direction, similar to the permanent magnet 32 ​​shown in FIG. 3.

[0115] Furthermore, similar to the magnet member 31 in the first and second embodiments, the permanent magnet 35 may be provided with a separation portion 36 that is separated from the outer peripheral surface 13b of the input shaft 13. In this case, as shown in Fig. 6, the separation portion 36 of the permanent magnet 35 is formed to extend from the position of the connection portion 15 toward the side where the press-fit portion 14 is located in the axial direction of the input shaft 13, and it is preferable that at least a portion of the press-fit portion 14 is located inside the separation portion 36 in the radial direction.

[0116] The magnet member 31 can reduce the number of parts by directly connecting the permanent magnet 35 of the magnet member 31 to the connection portion 15 of the input shaft 13, thereby reducing the manufacturing cost.

[0117] Furthermore, even when the permanent magnet 35 is directly connected to the connection portion 15 of the input shaft 13, by forming a separation portion 36 in the permanent magnet 35 and positioning at least a portion of the press-fit portion 14 of the input shaft 13 radially inward of the separation portion 36 of the permanent magnet 35, the connection portion 15 and the press-fit portion 14 can be positioned axially differently from each other, while the depth of the input shaft side hole 13a can be reduced. This simplifies the cutting process for forming the input shaft side hole 13a in the input shaft 13, and also enables the permanent magnet 35 to be attached to the input shaft 13 while avoiding an increase in the diameter of the input shaft 13 due to the press-fitting of the torsion bar 17. As a result, breakage of the permanent magnet 35 used in the torque sensor 30 can be suppressed while reducing manufacturing costs.

[0118] Furthermore, in the first and second embodiments described above, the torsion bar 17 is connected to the output shaft 16 by the connecting pin 70, but the torsion bar 17 may be connected to the output shaft 16 by means other than the connecting pin 70. The torsion bar 17 may be connected to the output shaft 16 by, for example, being press-fitted into the output-shaft-side hole 16a.

[0119] Furthermore, in the first and second embodiments described above, the electric power steering device 10 is of a column assist type in which an auxiliary steering torque is applied to the steering shaft 12, but the electric power steering device 10 may be of a type other than the column assist type. The electric power steering device 10 may be of a single pinion type in which the pinion gear 85a is rotated by the driving force generated by the electric motor 91, or may be of a dual pinion type in which a second pinion gear is provided to apply the driving force generated by the electric motor 91 to the rack bar 85b from a position different from the pinion gear 85a.

[0120] 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.

[0121] 10 Electric power steering device 11 Steering wheel 12 Steering shaft 13 Input shaft 13a Input shaft side hole portion 13b Outer circumferential surface 14 Press-fit portion 15 Connection portion 16 Output shaft 16a Output shaft side hole portion 17 Torsion bar 17a, 17b Enlarged diameter portion 20 Housing 21 First housing 25 Second housing 30 Torque sensor 31 Magnet member 32, 35 Permanent magnet 33 Magnet sleeve 34, 36 Separation portion 40 Stator 43 Stator sleeve 50 Magnetic flux collecting yoke 55 Hall IC 60, 65 Bearing 70 Connecting pin 71 Torsion bar sleeve 75 Key lock collar 81, 83 Universal joint 82 Intermediate shaft 84 Stub shaft 85 Steering gear 85a Pinion gear 85b Rack bar 86 Tie rod 90 ECU 91 Electric motor 92 Reduction gear 94 Worm wheel 95 Vehicle speed sensor 99 Power supply device

Claims

1. An electric power steering device comprising: an input shaft having an input shaft side hole portion on the inside; an output shaft having an output shaft side hole portion on the inside; a torsion bar having one end located inside the input shaft side hole portion and the other end located inside the output shaft side hole portion connecting the input shaft and the output shaft; and a torque sensor having a magnet member having a permanent magnet and connected to the outer peripheral surface of the input shaft, wherein the input shaft has a press-fit portion into which the torsion bar is press-fitted into the input shaft side hole portion, and a connection portion of the input shaft where the magnet member is connected is located at a position in the axial direction of the input shaft different from that of the press-fit portion.

2. An electric power steering device as set forth in claim 1, wherein the magnet member has a magnet sleeve in which the permanent magnet is disposed, and the magnet sleeve is connected to the connection portion of the input shaft.

3. The electric power steering device according to claim 1, wherein the permanent magnet of the magnet member is connected to the connection portion of the input shaft.

4. An electric power steering device as claimed in claim 2 or 3, wherein the magnet member has a separation portion extending in the axial direction from the position of the connection portion to the side where the press-fit portion is located and separated from the outer circumferential surface of the input shaft, and at least a portion of the press-fit portion is located inside the separation portion in the radial direction of the input shaft.

5. An electric power steering device according to any one of claims 1 to 4, wherein the press-fit portion is located on the output shaft side relative to the position of the connection portion in the axial direction.

6. An electric power steering device according to any one of claims 1 to 5, wherein a torsion bar sleeve is disposed between the output shaft side hole portion and the torsion bar disposed inside the output shaft side hole portion.

7. An electric power steering device as claimed in claim 6, comprising: a housing in which the input shaft and the output shaft are arranged; and a bearing which supports the output shaft rotatably relative to the housing, at least a portion of which is arranged at the same position in the axial direction as the position of the torsion bar sleeve.

8. An electric power steering device as claimed in any one of claims 1 to 7, wherein a key lock collar of a locking device that restricts rotation of the input shaft is disposed on the outer circumferential surface of the input shaft, and the key lock collar is disposed at a position in the axial direction different from that of the press-fit portion.

9. An electric power steering device according to any one of claims 1 to 8, wherein a connecting pin is disposed on the output shaft to connect the torsion bar, which is disposed inside the output shaft side hole portion, to the output shaft.

10. A method for manufacturing an electric power steering device comprising: an input shaft having an input shaft side hole portion on the inside; an output shaft having an output shaft side hole portion on the inside; a torsion bar having one end disposed inside the input shaft side hole portion and the other end disposed inside the output shaft side hole portion, connecting the input shaft and the output shaft; and a torque sensor having a magnetic member connected to the outer peripheral surface of the input shaft, wherein the input shaft has a press-fit portion into which the torsion bar is press-fitted into the input shaft side hole portion, wherein the press-fit portion of the input shaft is formed by forging, and a connection portion which connects the magnetic member on the input shaft is positioned in the axial direction of the input shaft different from the position of the press-fit portion.

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