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

Abstract

To prevent breakage of a permanent magnet used for a torque sensor.SOLUTION: An electric power steering device includes: an input shaft 13 having an input-shaft-side hole portion 13a on an inner side thereof; an output shaft 16 having an output-shaft-side hole portion 16a on an inner side thereof; a torsion bar 17 one-end side of which is disposed inside the input-shaft-side hole portion 13a and the other-end side of which is disposed inside the output-shaft-side hole portion 16a, and which connects the input shaft 13 and the output shaft 16; and a torque sensor 30 with a magnet member 31 having a permanent magnet 32 and connected to an outer peripheral surface 13b of the input shaft 13. The input shaft 13 includes a press-fit portion 14 in which the torsion bar 17 is press-fitted into the input-shaft-side hole portion 13a. A connection portion 15, which is a portion of the input shaft 13 to which the magnet member 31 is connected, is located at a position different from the press-fit portion 14 in the axial direction of the input shaft 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

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

[0003] For example, in the 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 end of the torsion bar is fixed to the output shaft by a fixing pin, and a torque sensor unit is provided on the vehicle rear side of the output shaft. Also, in the steering device described in Patent Document 2, the torsion bar fits into a hole provided in the center of the input shaft and is fixed to the input shaft via a pin, and the torsion bar is fixed to the output shaft by being press-fitted into a hole provided in the center of 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-27350 A [Patent Document 2] International Publication No. 2019 / 059230 Summary of the Invention [Problem to be solved by the invention]

[0005] A permanent magnet is used in the torque sensor used in the electric power steering device, and the permanent magnet is arranged on the input shaft or the output shaft. However, since the permanent magnet has low ductility, it is considered that the permanent magnet may break when the shaft to which the permanent magnet is attached is elastically deformed. For example, when a permanent magnet is attached directly or via a sleeve to the outer peripheral surface of the press-fitted portion of the torsion bar in the input shaft, and the torsion bar is press-fitted into the input shaft, the input shaft bulges slightly due to the press-fitting of the torsion bar, and the diameter of the input shaft increases slightly. In this case, the permanent magnet attached directly or via a sleeve to the outer peripheral surface of the input shaft cannot follow the bulge of the input shaft, and may break. In this way, when the permanent magnet breaks, the torque sensor cannot detect the steering torque, so there is room for improvement in terms of the arrangement of the permanent magnet in the electric power steering device having the torque sensor.

[0006] The present disclosure has been made in consideration of the above, and aims to provide an electric power steering device and a manufacturing method for an electric power steering device that can suppress breakage of a permanent magnet used in a torque sensor. [Means for solving the problem]

[0007] The electric power steering device disclosed herein 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 side arranged inside the input shaft side hole portion and the other end side arranged 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 which is the portion of the input shaft to which the magnet member is connected is located at a different position in the axial direction of the input shaft from the press-fit portion.

[0008] According to this configuration, since the axial position of the connection portion to which the magnet member is connected on the input shaft is different from the press-fit portion, even if the diameter of the input shaft becomes slightly larger 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 caused by the press-fitting of the torsion bar. As a result, breakage 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 connection portion of the input shaft.

[0010] According to this configuration, since the magnet sleeve in which the permanent magnet is disposed is connected to the connection portion of the input shaft, it is possible to minimize the force acting on the permanent magnet when disposing the magnet member on the input shaft. In other words, it is possible to minimize the stress generated in the permanent magnet when disposing the magnet member on the input shaft. As a result, it is possible to suppress breakage of the permanent magnet used in the torque sensor.

[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, since the permanent magnet of the magnet member is directly connected to the connection portion of the input shaft, the number of parts can be reduced, and as a result, the manufacturing cost can be reduced.

[0013] In a preferred embodiment, the magnet member has a separation portion extending in the axial direction from the position of the connection portion toward the side where the press-fit portion is located and separated 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] According to 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 that the depth of the input shaft side hole into which the torsion bar is press-fitted can be made shallow while the connection portion to which the magnet member of the input shaft is connected and the press-fit portion are made different in the axial direction. This simplifies the cutting process for forming 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 suppress 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 than the connection portion in the axial direction.

[0016] According to this configuration, the press-fitting portion of the input shaft into which the torsion bar is press-fitted is located closer to the output shaft than the connecting portion of the input shaft that connects the magnet member, so that the depth of the input shaft side hole from the end of the input shaft can be made shallower. This makes it possible to reduce the cutting range when forming the input shaft side hole by cutting the input shaft, and the cutting process when forming the input shaft side hole can be performed easily. In addition, by making the depth of the input shaft side hole from the end of the input shaft shallower, the distance by which the torsion bar is pressed into the input shaft side hole can be shortened when the torsion bar is press-fitted into the input shaft side hole. This improves the ease of assembly when assembling the torsion bar to the input shaft, and improves the workability in the assembly process. As a result, the manufacturing cost can be reduced.

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

[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 in the output-shaft-side hole portion. This makes it possible to suppress the torsion bar from collapsing in 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, the torsion bar can be supported by the torsion bar sleeve to suppress the torsion bar from collapsing in the output-shaft-side hole portion while press-fitting the torsion bar into the input-shaft-side hole portion. As a result, the ease of assembly of the electric power steering device can be improved.

[0019] In a preferred embodiment, the torsion bar drive mechanism includes a housing having the input shaft and the output shaft disposed therein, and a bearing having at least a portion of its position in the axial direction that is positioned at the same position as the torsion bar sleeve, and supporting the output shaft rotatably relative to the housing.

[0020] According to this configuration, the bearing that rotatably supports the output shaft is arranged at least partially at the same position in the axial direction as the torsion bar sleeve, so that the load acting on the torsion bar sleeve from the torsion bar can be received by the bearing arranged at a short distance from the torsion bar sleeve. This makes it possible to reduce the load acting on the bearing, and to suppress the difficulty in relative rotation between the inner ring and the outer ring of the bearing due to a large radial load acting on the bearing. Therefore, it is possible to suppress the increase in rotation resistance when rotating the output shaft supported by the bearing, and to reduce the rotation resistance when rotating the steering shaft having the output shaft. As a result, it is possible to reduce the steering torque when steering by rotating the steering wheel, and to improve 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 arranged on the outer peripheral surface of the input shaft, and the key lock collar is arranged at a position in the axial direction different from the press-fit portion.

[0022] According to this configuration, the key lock collar is disposed at a position different from the press-fit portion in the axial direction, so that the press-fit portion of the key lock collar and the input shaft can be prevented from being at the same position in the axial direction as the press-fit portion of the torsion bar in the input shaft. Therefore, it is possible to prevent the fitting force of the key lock collar with respect to the input shaft from changing from the fitting force set at the time of design, which is caused by the diameter of the input shaft becoming slightly larger at the position of the press-fit portion when the torsion bar is press-fitted into the input shaft side hole. This makes it possible to prevent the slip torque, which is the torque that causes the key lock collar to rotate relative to the input shaft when a force in a direction that rotates the input shaft and the key lock collar relative to each other is applied to the key lock collar, from changing from the set slip torque. Therefore, it is possible to prevent the key lock collar from rotating relative to the input shaft with an unexpectedly small torque, and the key lock collar can be properly fitted to the input shaft. As a result, the locking device having the key lock collar can be properly operated.

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

[0024] According to this configuration, the torsion bar is not press-fitted into the output shaft but is connected by a connecting pin, so that the axial force applied to the torsion bar can be reduced when the torsion bar is inserted into the output shaft side hole and connected to the output shaft. This makes it possible to suppress buckling of the torsion bar caused by a large axial force being applied to the torsion bar from a position away from the press-fit portion of the torsion bar into the output shaft. This improves the ease of assembly when assembling the torsion bar to the output shaft, and improves the workability of the assembly process. As a result, the manufacturing cost can be reduced.

[0025] The manufacturing method for an electric power steering device disclosed herein 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 having one end side arranged inside the input shaft side hole portion and the other end side arranged 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, 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, so that the rigidity of the press-fit portion can be increased. 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 portion of the input shaft, can be strengthened, and the input shaft and the torsion bar can be prevented from rotating relative to each other when a steering torque is applied to the input shaft. As a result, the steering torque applied to the input shaft can be appropriately transmitted to the output shaft via the torsion bar, and the input shaft and the output shaft can be rotated relative to each other by a slight twist of the torsion bar according 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 the torque sensor. As a result, the magnitude of the steering torque input to the input shaft can be appropriately detected. Effect of the Invention

[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 breakage of the permanent magnet used in the torque sensor. [Brief description of the drawings]

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

[0029] Hereinafter, the present disclosure will be described in detail 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 a person skilled in the art can easily imagine, 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 appropriately combined.

[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 of transmission of force applied by an operator, 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 is referred to as the "axial direction", and the direction intersecting (perpendicular to) the axial direction is 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 by 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 a 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 of them.

[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 joint 81 and the universal joint 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 the stub shaft 84. One end of the stub shaft 84 is connected to the universal joint 83, and the other end is connected to the 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 joint 81 and the universal joint 83. The universal joint 81 and the universal joint 83 are, for example, a Cardan joint. The 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. That is, 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 each of 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 value 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. The ECU 90 controls the electric motor 91, thereby reducing the force required to operate the steering wheel 11.

[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 have the same central 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 in a direction 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 which 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 portion 16a and a connecting hole 16b extending in the axial direction on the radially inner side. The output shaft 16 is located on the side of the input shaft 13 where the end of the input shaft 13 where the input shaft side hole portion 13a is formed is located. The output shaft 16 is rotatable in the direction around the central axis AX. The connecting hole 16b has an inner diameter larger than that of the output shaft side hole portion 16a, and is formed at a predetermined depth from the end of the output shaft 16 on the side where the input shaft 13 is connected to the side opposite the side where the input shaft 13 is located. The output shaft side hole portion 16a extends from the end of the connecting hole 16b of the output shaft 16 toward the side opposite the side where the input shaft 13 is located. A portion near the end of the input shaft 13 is inserted into the inside of 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 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 disposed on the outer periphery of the core metal portion 94a integrally with the core metal portion 94a. The worm wheel 94 is fixed to the output shaft 16 by pressing 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 increases the torque of the driving force generated by the electric motor 91 and transmits it to the output shaft 16, thereby providing the output shaft 16 with an auxiliary steering torque. 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 disposed inside the input shaft side hole 13a of the input shaft 13 has a portion near its end pressed into the input shaft side hole 13a. As a result, the torsion bar 17 is fixed to the input shaft 13 while being subjected to relative rotation.

[0042] More specifically, the torsion bar 17 has an expanded diameter portion 17a formed near the end portion of the torsion bar 17 located on the inside of the input shaft side hole portion 13a of the input shaft 13. The expanded diameter portion 17a is located within a predetermined axial range from the end portion of the torsion bar 17 located on the inside of the input shaft side hole portion 13a, and has a diameter slightly larger than the inner diameter of the input shaft side hole portion 13a. The expanded diameter portion 17a has a larger diameter than the other portions of the torsion bar 17 than the expanded diameter portion 17a, and the other portions of the torsion bar 17 than the expanded diameter portion 17a have a smaller diameter than the inner diameter of the input shaft side hole portion 13a. The expanded diameter portion 17a is press-fitted into the input shaft side hole portion 13a of the input shaft 13, whereby the torsion bar 17 is press-fitted and fixed into the input shaft side hole portion 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 portion 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 portion 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 portion 13a into which the torsion bar 17 is press-fitted.

[0044] A portion of the torsion bar 17 that is disposed on the inside of 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, disposed on the inside of the output-shaft-side hole 16a, and the output shaft 16.

[0045] In detail, a through hole penetrating in the radial direction is formed at the end of the torsion bar 17 on the side inserted into the output shaft side hole 16a of the output shaft 16. The torsion bar 17 also has an enlarged diameter portion 17b formed near the end on the side disposed inside the output shaft side hole 16a of the output shaft 16, and the through hole is formed in the enlarged diameter portion 17b. Also, a through hole penetrating in the radial direction is formed at the position in the axial direction of the output shaft 16 where the through hole of the torsion bar 17 is formed. The through hole formed in the enlarged 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 on the side 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] In addition, 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 disposed inside the output-shaft-side hole 16a at a position toward 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 approximately equal to 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. In addition, 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 portion on the end side where the enlarged diameter portion 17b through which the connecting pin 70 passes is located.

[0047] The torsion bar sleeve 71 thus formed is fitted into the output shaft side hole 16a on the inside of the output shaft side hole 16a, and the torsion bar 17 is disposed inside the output shaft side hole 16a 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 on the inside of the torsion bar sleeve 71 is smaller than any 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 is a housing for 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, and 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 is also provided 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 with respect to the first housing 21. The bearing 65 is provided as a second bearing that rotatably supports the output shaft 16 with respect to the second housing 25.

[0050] The bearing 60 and the bearing 65 are disposed on both sides in the axial direction of the position on the output shaft 16 where the worm wheel 94 is fixed. The bearing 60 is disposed on the side where the input shaft 13 is located in the axial direction with respect to the position where the core metal portion 94a of the worm wheel 94 on the output shaft 16 is fixed, and the bearing 65 is disposed on the opposite side in the axial direction to the side where the input shaft 13 is located, with respect to the position where the core metal portion 94a of the worm wheel 94 is fixed. In other words, the bearing 65 is disposed on the opposite side in the axial direction to the side where the bearing 60 is located with respect to 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 of 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 to each other in the axial direction with respect to the radial protrusion 16c. As a result, the bearing 60 and the bearing 65 are disposed on opposite sides to each other in the axial direction with respect to the worm wheel 94.

[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 for explaining an overview of the permanent magnet 32, the stator 40, and the magnetic flux collecting yoke 50 of the torque sensor 30. One of the permanent magnet 32 ​​and the 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 N poles and S poles are alternately arranged 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 the 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 the thickness direction of the plate being oriented in the radial direction of the flange portion 41. The teeth portions 42 are arranged side by side in the circumferential direction of the flange portion 41 with a gap therebetween.

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

[0057] That is, the first stator 40a is arranged with the first teeth 42a extending from the first flange 41a toward the second stator 40b, and the second stator 40b is arranged with the second teeth 42b extending from the second flange 41b toward the first stator 40a. At this time, since the first teeth 42a and the second teeth 42b are each provided in a plurality 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 the stator 40 are located in a portion in 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 40a and the second stator 40b thus combined. The permanent magnet 32 ​​and the stator 40 are disposed in such a manner that their axial directions coincide with the axial directions of the input shaft 13 and the output shaft 16. For this reason, the permanent magnet 32 ​​and the stator 40 are attached to the input shaft 13 and the output shaft 16 in such a positional relationship that the outer peripheral surface of the permanent magnet 32 ​​faces the teeth 42 of the stator 40. By disposing the permanent magnet 32 ​​and the stator 40 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 magnetic flux acting on the stator 40 from the permanent magnet 32 ​​changes as the relative positional relationship between the permanent magnet 32 ​​and the stator 40 changes.

[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 member for detecting a change in the magnetic flux acting on the stator 40 from the permanent magnet 32, and is disposed near the flange portion 41 of the stator 40. Since the stator 40 includes a pair of a first stator 40a and a second stator 40b, the magnetic flux collecting yoke 50 also includes 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 magnetic flux collecting yoke 50 includes a first magnetic flux collecting yoke 50a disposed near the first flange portion 41a of the first stator 40a, and a second magnetic flux collecting yoke 50b 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 side 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 side of the second flange portion 41b of the second stator 40b where the first flange portion 41a is located. In this way, the magnetic flux collecting yoke 50 is located near the flange portions 41, so that the magnetic flux collecting yoke 50 can detect a change 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 magnetism collecting yokes 50. The Hall IC 55 is disposed between the magnetism collecting yokes 50 at a position away from a portion of the magnetism collecting yoke 50 located near the flange portion 41 of the stator 40. The Hall IC 55 is capable of detecting a change in the magnetic flux density acting on the two magnetism collecting yokes 50, converting the detected change in the magnetic flux density into an electric signal, and outputting the electric signal. Note that a magnetic sensor that applies 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 magnetism 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, for example, fixed to 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 with the pair of magnetism collecting yokes 50 positioned between two flange portions 41 of the stator 40 and the Hall IC 55 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 the permanent magnet 32 ​​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 to which 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 a portion of the outer circumferential surface 13b of the input shaft 13 to which the magnet member 31 is connected and attached. 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] Further, the magnet member 31 attached to the input shaft 13 has a separation portion 34 separated from the outer circumferential surface 13b of the input shaft 13. The separation portion 34 is located at a position in the axial direction different from the connection portion 15, and in the first embodiment, the separation portion 34 is located on the side of the connection portion 15 where the output shaft 16 is located in the axial direction. 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 position in the axial direction of 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 magnet member 31 has an inner diameter that is the same at the position of the connecting portion 15 and at 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 at 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 located at a position in the axial direction of the input shaft 13 that is different from the position of the press-fit portion 14. When the magnet member 31 is attached to the input shaft 13 during the 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 position in the axial direction 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 portion 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 to 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 the stator sleeve 43 and the carrier 44. The stator sleeve 43 is a cylindrical member, and the output shaft 16 is press-fitted into the stator sleeve 43 to attach the stator sleeve 43 to the output shaft 16. 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 attached to the output shaft 16 by the stator sleeve 43 is supported by the stator sleeve 43 and disposed at a position from the output shaft 16 toward the input shaft 13, and disposed at a radially outer position of the input shaft 13. Furthermore, the carrier 44 is disposed at the same position in the axial direction as the permanent magnet 32 ​​of the magnet member 31, and disposed radially outward of the permanent magnet 32.

[0071] The stator 40 is attached to the carrier 44 arranged in this manner. In detail, each of the first stator 40a and the second stator 40b is attached to the carrier 44 with the teeth portion 42 located on the radially inner side of the carrier 44 and the flange portion 41 protruding from the radially inner side to the radially outer side 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 arranged on the radially outer side of the permanent magnet 32.

[0072] 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 together with the output shaft 16. The stator 40 thus arranged to be rotatable together with the output shaft 16 has, in other words, a flange portion 41 protruding 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] Also, a key lock collar 75 of a lock device (not shown) that restricts the 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 circumferential 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 lock device that restricts the rotation of the steering shaft 12 restricts the rotation of the input shaft 13 of the steering shaft 12. The input shaft 13 is press-fitted into the key lock collar 75, and the key lock collar 75 is attached so as to be unable to rotate relative to the input shaft 13. For example, when the driver of the vehicle removes the key, the lock device has a pin that protrudes from the housing 20 toward the key lock collar 75 and fits into the key lock collar 75. As a result, the housing 20 and the input shaft 13 are fixed so as not to rotate relative to each other, and the steering wheel 11 cannot be rotated when the key is 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 supports the output shaft 16 rotatably 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 parts 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 the step portion 23 restricts the bearing 60 from moving relative to the first housing 21 in the axial direction.

[0076] Moreover, at least a portion of the bearing 60 is disposed at the same position in the axial direction as the position of 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 being disposed at the same position in the axial direction as the position of 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 supports the output shaft 16 rotatably relative 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 to the output shaft 16 and its outer circumferential surface to the second housing 25, and supports the output shaft 16 rotatably relative to the second housing 25. A protruding portion 27 that protrudes radially inward is formed on the inner circumferential surface 26 of the second housing 25 into which the bearing 65 fits, and the bearing 65 abuts against the protruding portion 27 in the axial direction. As a result, the bearing 65 fits into the second housing 25 in a state in which relative movement in the axial direction with respect to the second housing 25 is restricted by the protruding portion 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, and operates the tie rod 86.

[0079] The electric power steering device 10 according to the first embodiment also has 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 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 a 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] That is, 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. Also, 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 with each other at the position where they are 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 where they are 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, so that 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 on the stator 40 from the permanent magnet 32 ​​changes. The magnetic flux collecting yoke 50 arranged in the vicinity of the stator 40 is capable of detecting the change in the magnetic flux acting on the stator 40 from the permanent magnet 32. Therefore, when the permanent magnet 32 ​​and the stator 40 rotate relative to each other in accordance with the relative rotation of the input shaft 13 and the output shaft 16, the magnetic flux collecting yoke 50 arranged in the vicinity of the stator 40 can detect the change in the magnetic flux acting on the stator 40 from the permanent magnet 32.

[0085] In this way, the magnetic flux acting on the stator 40 from the permanent magnet 32, which is detected by the magnetic flux collecting yoke 50, changes according to the angle of relative rotation between the permanent magnet 32 ​​and the stator 40. The Hall IC 55 detects the magnetic flux, which changes according to the angle of relative rotation between the permanent magnet 32 ​​and the stator 40 detected by the magnetic flux collecting yoke 50, with a Hall element, converts it into an electric signal with an output circuit, and transmits it 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 ​​with the magnetic flux 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 electric signal transmitted from the torque sensor 30, and causes the electric motor 91 to generate an auxiliary steering torque. In other words, the electric 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. For this reason, the ECU 90 uses the electric 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, adjusts the value of the power supplied to the electric motor 91 based on the electric signal transmitted from the Hall IC 55, and causes the electric motor 91 to generate an auxiliary steering torque.

[0087] That is, the ECU 90 obtains a steering torque signal from the torque sensor 30, obtains a vehicle speed signal from the vehicle speed sensor 95, and further obtains operation information of the electric motor 91 from a rotation detection device provided in the electric motor 91. Based on the operation information, steering torque, and vehicle speed signal, the ECU 90 causes the electric motor 91 to generate an auxiliary steering torque. 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) connected to the output shaft of the electric motor 91 and a worm wheel 94. 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-fitting portion 14, and the magnet member 31 of the torque sensor 30 has a connection portion 15, which is a portion of the input shaft 13 to which the magnet member 31 is connected, and the position of the press-fitting portion 14 in the axial direction. As a result, even if the diameter of the input shaft 13 becomes slightly larger at the position of the press-fitting 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 ​​having low ductility can be attached to the input shaft 13 while avoiding the increase in the diameter of the input shaft 13 caused by the press-fitting of the torsion bar 17. As a result, the breakage 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 the force acting on the permanent magnet 32 ​​when disposing the magnet member 31 on the input shaft 13 can be minimized. In other words, the stress generated in the permanent magnet 32 ​​when disposing the magnet member 31 on the input shaft 13 can be minimized. As a result, breakage of the permanent magnet 32 ​​used in the torque sensor 30 can be suppressed.

[0090] In addition, since the 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 suppress the torsion bar 17 from falling into 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, the torsion bar 17 can be supported by the torsion bar sleeve 71 and the torsion bar 17 can be press-fitted into the input-shaft-side hole 13a while suppressing the torsion bar 17 from falling into the output-shaft-side hole 16a. As a result, the ease of assembly of the electric power steering device 10 can be improved.

[0091] In addition, the bearing 60, which rotatably supports the output shaft 16 relative to the housing 20, is arranged at least partially at the same position in the axial direction as the position of the torsion bar sleeve 71, so that the load acting from the torsion bar 17 on the torsion bar sleeve 71 can be efficiently received by the bearing 60. In other words, the load acting from the torsion bar 17 on the torsion bar sleeve 71 can be received by the bearing 60, which is arranged at a short distance from the torsion bar sleeve 71. This makes it possible to reduce the load acting on the bearing 60, and to suppress the relative rotation between the inner ring and the outer ring of the bearing 60 becoming difficult due to the large radial load acting on the bearing 60. Therefore, it is possible to suppress the increase in rotation resistance when rotating the output shaft 16 supported by the bearing 60, and to reduce the rotation resistance when rotating the steering shaft 12 having the output shaft 16. As a result, it is possible to reduce the steering torque when steering by rotating the steering wheel 11, and to improve the operability of the electric power steering device 10.

[0092] Furthermore, since the output shaft 16 is provided with a connecting pin 70 that connects the torsion bar 17 disposed inside the output shaft side hole portion 16a to the output shaft 16, it is possible to prevent buckling of the torsion bar 17. In other words, when the torsion bar 17 press-fitted into the input shaft 13 is also press-fitted into the output shaft 16, the position at which an axial force is applied to the torsion bar 17 tends to be away from the portion of the torsion bar 17 that is press-fitted into the output shaft 16. In this case, it is considered that buckling of the torsion bar 17 occurs due to the large 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 makes it possible to suppress the occurrence of buckling of the torsion bar 17 caused by a large axial force being applied to the torsion bar 17 from a position away from the press-fit portion of the torsion bar 17 to the output shaft 16. This improves the ease of assembly when assembling the torsion bar 17 to the output shaft 16, and improves the workability in the assembly process. As a result, the manufacturing cost can be reduced.

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

[0095] 4 is a cross-sectional view of a main part 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 located at a position different from the press-fit portion 14 in the axial direction of the input shaft 13.

[0096] In the second embodiment, unlike the first embodiment, the connection portion 15 to which the magnet member 31 of the input shaft 13 is connected is located on the opposite side to the output shaft 16 with respect to the position of the press-fit portion 14 in the axial direction. That is, the press-fit portion 14 of the torsion bar 17 in the input shaft 13 is located closer to the output shaft 16 than the position of the connection portion 15 in the axial direction. In detail, the press-fit portion 14 is located slightly closer to the output shaft 16 than the position of the connection portion 15 without having a portion whose position in the axial direction is near the position of the connection portion 15 and whose position in the axial direction is the same as that of the connection portion 15.

[0097] In the second embodiment, the magnet member 31 has a separation portion 34 separated from the outer circumferential surface 13b of the input shaft 13, which extends from the position of the connection portion 15 to 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, whose axial position is located 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 at the same position as the axial position of the separation portion 34 of the magnet member 31.

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

[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 opposite side 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 of the electric power steering device 10 according to the second embodiment, forging is performed from the outer peripheral surface 13b side in the range in the axial direction of the input shaft 13 where the press-fit portion 14 is formed. The input shaft 13 has the forged press-fit portion 14. In addition, the input shaft side hole portion 13a is cut from the end side of the input shaft 13 on the side where the output shaft 16 is located, with respect to the press-fit portion 14 of the input shaft 13 forged from the outer peripheral surface 13b side. As a result, the rigidity of the outer peripheral surface 13b side of the press-fit portion 14 of the input shaft 13 is improved, and the input shaft side hole portion 13a into which the torsion bar 17 is press-fitted is formed with high accuracy.

[0101] Fig. 5 is a detailed view of part A in Fig. 4. The torsion bar 17 press-fitted into the input shaft side hole 13a formed in the press-fitting portion 14 of the input shaft 13 has a push-in portion 17c formed in the portion of the torsion bar 17 on the side where the output shaft 16 is located in the expanded diameter portion 17a press-fitted into the input shaft side hole 13a. The push-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 is 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 push-in portion 17c of the torsion bar 17 is a stepped portion with a diameter smaller than that of the expanded diameter portion 17a and a portion connected to the expanded diameter portion 17a, and the stepped portion 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 as well, a key lock collar 75 is disposed on the outer circumferential surface 13b of the input shaft 13. The key lock collar 75 is disposed at a position in the axial direction different from the press-fit portion 14, and the key lock collar 75 is disposed at a position opposite the side where the output shaft 16 is located with respect to the press-fit portion 14 in the axial direction. In other words, the key lock collar 75 is disposed at a position opposite the side where the output shaft 16 is located with respect to the magnet member 31 disposed on the input shaft 13 in the axial direction.

[0104] In the second embodiment, unlike the first embodiment, the keylock collar 75 is disposed on the outer circumferential surface 13b of the input shaft 13 via a slip ring 76. The slip ring 76 is in the form of a leaf spring formed in a substantially annular shape, and is disposed between the inner circumferential surface of the keylock collar 75 and the outer circumferential surface 13b of the input shaft 13. The slip ring 76 holds the keylock collar 75 on the outer circumferential surface 13b of the input shaft 13 while generating frictional forces between the inner circumferential surface of the keylock collar 75 and the outer circumferential surface of the slip ring 76, and between the outer circumferential surface 13b of the input shaft 13 and the inner circumferential surface of the slip ring 76, due to the elastic force of the leaf spring.

[0105] When a large force is input in a direction that rotates the keylock collar 75 and the input shaft 13 relative to each other, the slip ring 76 arranged in this manner slips to allow relative rotation between the keylock collar 75 and the input shaft 13. For this reason, when a large force equal to or greater than a predetermined value is input in a direction that rotates the keylock collar 75 and the input shaft 13 relative to each other, the keylock collar 75 is arranged to be rotatable relative to the input shaft 13 due to slippage 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 press-fit portion 14, into which the torsion bar 17 of the input shaft 13 is press-fitted. Therefore, the permanent magnet 32 ​​of the magnet member 31, which 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, breakage 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 in the axial direction of the input shaft 13 closer to the output shaft 16 than the connection portion 15, which connects the magnet member 31 to 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 the cutting range required to form the input shaft side hole 13a by cutting the input shaft 13 can be reduced. This simplifies the cutting process required to form 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 shallow, the distance by which the torsion bar 17 is pressed into the input shaft side hole 13a can be shortened when the torsion bar 17 is press-fitted 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 improves the workability in the assembly process. As a result, the manufacturing cost can be reduced.

[0109] In addition, since the torsion bar 17 has a 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 portion 13a of the input shaft 13, the torsion bar 17 can be easily press-fitted into the input shaft side hole portion 13a by applying a load to the push-in portion 17c. This makes it possible to prevent the torsion bar 17 from buckling due to the application of a load to a position away from the enlarged diameter portion 17a of the torsion bar 17 when the torsion bar 17 is press-fitted into the input shaft side hole portion 13a of the input shaft 13. Therefore, it is possible to improve the ease of assembly when assembling the torsion bar 17 to the input shaft 13, and to improve the workability in the assembly process. As a result, it is possible to reduce the manufacturing cost.

[0110] In addition, since at least a portion of the press-fit portion 14 of the input shaft 13 is located radially inside the separation portion 34 of the magnet member 31, the depth of the input shaft side hole 13a into which the torsion bar 17 is press-fitted can be made shallow while making the axial positions of the connection portion 15 to which the magnet member 31 of the input shaft 13 is connected and the press-fit portion 14 different. 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-fit of the torsion bar 17. As a result, the manufacturing cost can be reduced and breakage of the permanent magnet 32 ​​used in the torque sensor 30 can be suppressed.

[0111] In addition, since 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, the connection between the input shaft 13 and the torsion bar 17, which are connected by press-fitting the torsion bar 17 into the input shaft side hole portion 13a of the input shaft 13, can be strengthened, and the input shaft 13 and the torsion bar 17 can be prevented from rotating relative to each other when a steering torque is applied to the input shaft 13. As a result, the 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 according 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] In addition, 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, so that the portion where the key lock collar 75 is disposed on the input shaft 13 via the slip ring 76 can be prevented from being at the same axial position as the press-fit portion 14 of the torsion bar 17 on the input shaft 13. This can prevent the fitting force of the key lock collar 75 via the slip ring 76 to the input shaft 13 from changing from the fitting force set at the time of design, which is 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 portion 13a of the input shaft 13. This can prevent the slip torque, which is a torque of a magnitude that causes the key lock collar 75 to rotate relative to the input shaft 13 when a force in a direction that rotates the input shaft 13 and the key lock collar 75 relative to each other, from changing from the set slip torque. 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 the key lock collar 75 can be properly fitted to the input shaft 13. As a result, the locking device having the key lock collar 75 can be properly operated.

[0113] [Variations] In the first and second embodiments described above, the magnet member 31 connected to the input shaft 13 has a magnet sleeve 33, and a 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] FIG. 6 is a cross-sectional view of a main part 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 composed of a permanent magnet 35 alone, 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 formed in a substantially cylindrical shape and having a plurality of N poles and S poles alternately arranged in the circumferential direction, similar to the permanent magnet 32 ​​shown in FIG. 3.

[0115] Similarly to the magnet member 31 in the first and second embodiments, the permanent magnet 35 may be provided with a separation portion 36 separated from the outer circumferential surface 13b of the input shaft 13. In this case, the separation portion 36 of the permanent magnet 35 is formed to extend from the position of the connection portion 15 to the side where the press-fit portion 14 is located in the axial direction of the input shaft 13, as shown in Fig. 6, 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 magnets 35 of the magnet member 31 to the connection portion 15 of the input shaft 13 as described above, thereby enabling a reduction in manufacturing costs.

[0117] Also, 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 part of the press-fit portion 14 of the input shaft 13 radially inside the separation portion 36 of the permanent magnet 35, the depth of the input shaft side hole 13a can be made shallow while making the positions of the connection portion 15 and the press-fit portion 14 different in the axial direction. This simplifies the cutting process for forming the input shaft side hole 13a in the input shaft 13, and the permanent magnet 35 can be attached to the input shaft 13 while avoiding an increase in the diameter of the input shaft 13 due to the press-fit of the torsion bar 17. As a result, the manufacturing cost can be reduced and breakage of the permanent magnet 35 used in the torque sensor 30 can be suppressed.

[0118] In addition, in the above-described first and second embodiments, 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 something 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 portion 16a.

[0119] 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 having a second pinion gear that applies 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. [Explanation of symbols]

[0121] 10. Electric power steering device 11 Steering wheel 12 Steering shaft 13 Input shaft 13a Input shaft side hole 13b Outer surface 14 Press-fit section 15 Connection 16 Output shaft 16a Output shaft side hole 17 Torsion bar 17a, 17b Expanded diameter part 20. Housing 21 1st Housing 25 Second Housing 30 Torque Sensor 31 Magnet parts 32, 35 Permanent magnets 33 Magnetic Sleeve 34, 36 Separation part 40 Stator 43 Status Leave 50 Magnetic field collector 55 Hall IC 60, 65 Bearings 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 Reducer 94 Worm Wheel 95 Vehicle speed sensor 99 Power supply

Claims

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

2. the magnet member has a magnet sleeve in which the permanent magnet is disposed, The electric power steering device according to claim 1 , wherein 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. the magnet member has a separation portion extending from a position of the connection portion toward a side where the press-fit portion is located in the axial direction and separated from the outer circumferential surface of the input shaft, The electric power steering device according to claim 2 or 3, wherein at least a portion of the press-fit portion is located inside the separated portion in the radial direction of the input shaft.

5. The electric power steering device according to claim 1 , wherein the press-fit portion is located closer to the output shaft than the connection portion in the axial direction.

6. The electric power steering device according to claim 1 , wherein a torsion bar sleeve is disposed between the output shaft side hole and the torsion bar disposed inside the output shaft side hole.

7. a housing having the input shaft and the output shaft disposed therein; a bearing that is disposed at least at a portion of the axial direction at the same position as the torsion bar sleeve and that supports the output shaft rotatably relative to the housing; The electric power steering device according to claim 6 .

8. 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, The electric power steering device according to claim 1 , wherein the key lock collar is disposed at a position in the axial direction different from the press-fit portion.

9. The electric power steering device according to claim 1 , wherein a connecting pin is disposed on the output shaft, the connecting pin connecting the output shaft and the torsion bar disposed inside the output shaft side hole portion.

10. an input shaft having an input shaft side hole portion on an inner side; an output shaft having an output shaft side hole on an inner side; 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, the torsion bar connecting the input shaft and the output shaft; a torque sensor having a magnet member connected to an outer circumferential surface of the input shaft; Equipped with In a manufacturing method for an electric power steering device, the input shaft has a press-fit portion into which the torsion bar is press-fitted into the input shaft side hole portion, The press-fit portion of the input shaft is formed by forging, A manufacturing method for an electric power steering device, wherein a connection portion, which is a portion of the input shaft that connects the magnet member, is positioned in the axial direction of the input shaft differently from a position of the press-fit portion.

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