Electric power steering system

Abstract

To reduce a load acting on a connector held by a torque sensor and a case for the torque sensor, which holds the connector.SOLUTION: An electric power steering device 100 includes: an input shaft 13 into which steering torque is input; an output shaft 15 connected to the input shaft 13 via a torsion bar 14; a torque sensor 40 configured to detect the steering torque; a connector 49 held by a case 41 for the torque sensor 40 to be electrically connected to the torque sensor 40; a through-hole 61a formed to extend through an outer wall of a housing 5; and a cable 36 which is inserted into the through-hole 61a and electrically connects the connector 49 to an external device. The cable 36 includes a relaxation part 36 linearly extending from the through-hole 61a along an inner surface of the housing 5.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electric power steering device.

Background Art

[0002] Patent Document 1 discloses an electric power steering device including an input shaft, an output shaft, a torque sensor, a housing, a cable that electrically connects the torque sensor and a controller that controls driving of an electric motor, and a connector held in a case of the torque sensor and connected with the cable.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In the electric power steering device described in Patent Document 1, the cable electrically connected to the controller is bent along the inner wall surface of the housing inside the housing, and is further bent to be folded back in the vicinity of the connector.

[0005] When the cable is bent and connected to the connector in this manner, the restoring force of the cable applies a load to the connector and the case of the torque sensor that holds the connector, which may cause adverse effects.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to reduce the load acting on a connector and a case of a torque sensor that holds the connector in an electric power steering device.

Means for Solving the Problems

[0007] The present invention relates to an electric power steering device comprising: an input shaft to which steering torque is input; an output shaft connected to the input shaft via a torsion bar; a torque sensor mounted across the input shaft and the output shaft for detecting steering torque; a housing housing the input shaft, the output shaft, and the torque sensor; an electric motor that generates steering assist torque based on the detection result of the torque sensor; a connector held in the case of the torque sensor and electrically connected to the torque sensor; a through hole formed to penetrate the outer wall of the housing; and a cable inserted through the through hole for electrically connecting the connector to external equipment, wherein the cable is connected through the through hole. A linear shape is formed close to the inner circumferential surface of the cylindrical part of the housing in which it is formed. It has a relaxation section that extends to it. Furthermore, the connector is located in the area opposite the through-hole, straddling the input shaft, and the angle between the connection direction of the connector and the cable and the axis of the through-hole is approximately 90°. It is characterized by the following.

[0008] In this invention, the cable has a relaxation section that extends linearly from the through-hole along the inner surface of the housing. This eliminates the need to bend the cable to avoid the input shaft, thus reducing the amount of bending required. Furthermore, the relaxation section reduces the load caused by the cable's restoring force. Therefore, the load caused by the cable's restoring force acting on the connector and the case of the torque sensor that holds the connector can be reduced. Furthermore, in this invention, since the connector is located in the area opposite the through-hole, straddling the input shaft, the length of the cable within the housing can be increased. As a result, even if the cable is bent, the longer cable allows for some slack, thus mitigating the load caused by the cable's restoring force. Moreover, in this invention, the angle between the connection direction between the connector and the cable and the axis of the through-hole is approximately 90°, which minimizes the amount of cable bending and maximizes the length of the mitigation section that reduces the load caused by the cable's restoring force.

[0011] Furthermore, the present invention is characterized in that the connector and the through-hole are located on the same plane perpendicular to the rotation axis of the input shaft.

[0012] In this invention, by providing the connector and the through-hole on the same plane, the bending portion of the cable in the direction of the rotation axis of the input shaft can be eliminated.

[0013] Furthermore, the present invention is An electric power steering device comprising: an input shaft to which steering torque is input; an output shaft connected to the input shaft via a torsion bar; a torque sensor mounted across the input shaft and output shaft for detecting steering torque; a housing housing the input shaft, output shaft, and torque sensor; an electric motor that generates steering assist torque based on the detection result of the torque sensor; a connector held in the case of the torque sensor and electrically connected to the torque sensor; a through hole formed to penetrate the outer wall of the housing; and a cable inserted through the through hole for electrically connecting the connector to external equipment. A fixing member for securing the cable to the housing, The cable has a relieving portion that extends linearly close to the inner circumferential surface of the cylindrical part of the housing in which the through hole is formed, The cable further has a bent portion that connects the connector and the relaxation portion, and the fixing member is characterized by fixing the bent portion to the housing.

[0014] In this invention, The cable has a relief section that extends linearly from the through-hole along the inner surface of the housing. This eliminates the need to bend the cable to avoid the input shaft, thus reducing the amount of bending required. Furthermore, the relief section reduces the load caused by the cable's restoring force. Therefore, the load caused by the cable's restoring force acting on the connector and the case of the torque sensor that holds the connector can be reduced. Furthermore, in this invention, since the bent portion of the cable is fixed to the housing, the load acting on the connector and the case of the torque sensor that holds the connector can be reduced. [Effects of the Invention]

[0015] According to the present invention, the load caused by the restoring force of the cable acting on the connector and the case of the torque sensor that holds the connector can be reduced. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a diagram showing the configuration of an electric power steering device according to an embodiment of the present invention. [Figure 2] Figure 2 is an external view of the vicinity of the assist mechanism in an electric power steering device according to an embodiment of the present invention. [Figure 3] Figure 3 is a cross-sectional view of the vicinity of the assist mechanism in an electric power steering device according to an embodiment of the present invention. [Figure 4] Figure 4 is a plan view of the vicinity of the assist mechanism in an electric power steering device according to an embodiment of the present invention, and the first housing is not shown. [Figure 5] Figure 5 is an enlarged partial cross-sectional view of the vicinity of the torque sensor of the assist mechanism in an electric power steering device according to an embodiment of the present invention. [Figure 6] Figure 6 shows a comparative example of an assist mechanism in an electric power steering device according to an embodiment of the present invention. [Modes for carrying out the invention]

[0017] Hereinafter, an electric power steering device 100 according to an embodiment of the present invention will be described with reference to the drawings.

[0018] The electric power steering system 100 is mounted on the vehicle and assists the driver in steering the steering wheel 1.

[0019] In the present embodiment, as shown in Figure 1, a single-pinion type electric power steering apparatus 100 in which steering torque by a driver and steering assist torque by an electric motor 21 are input to a rack shaft 12 will be described.

[0020] First, the overall configuration of the electric power steering apparatus 100 will be described with reference to Figure 1.

[0021] The electric power steering apparatus 100 includes a steering mechanism 10 that steers wheels 2 in response to rotation of a steering wheel 1 caused by driver steering, an assist mechanism 20 that assists driver steering, a torque sensor 40 that detects steering torque input by the driver through the steering wheel 1, and a controller 30 that controls driving of an electric motor 21 based on a detection result of the torque sensor 40.

[0022] The steering mechanism 10 has a steering shaft 11 that rotates in response to rotation of the steering wheel 1, and a rack shaft 12 that steers the wheels 2 in response to rotation of the steering shaft 11.

[0023] The steering shaft 11 has an input shaft 13 that rotates as the driver steers the steering wheel 1, an output shaft 15 linked to the rack shaft 12 that steers the wheels 2, and a torsion bar 14 that connects the input shaft 13 and the output shaft 15.

[0024] A pinion 16 that meshes with the rack 12a formed on the rack shaft 12 is formed at the lower part of the output shaft 15. When the steering wheel 1 is steered, the steering shaft 11 rotates, and this rotation is converted into linear motion of the rack shaft 12 by the pinion 16 and the rack 12a, causing the wheel 2 to turn via the knuckle arm 4. Alternatively, instead of forming the pinion 16 at the lower part of the output shaft 15, the pinion shaft that meshes with the rack shaft 12 and the output shaft 15 may be connected via an intermediate shaft.

[0025] The assist mechanism 20 includes an electric motor 21 which is the power source for steering assist torque, an output shaft 22 to which the driving force of the electric motor 21 is transmitted, and a reduction mechanism 3 which reduces the rotation of the electric motor 21 and transmits it to the output shaft 15. The reduction mechanism 3 includes a worm shaft 3a connected to the output shaft 22 of the electric motor 21, and a worm wheel 3b which meshes with the worm shaft 3a and is fixed to the output shaft 15.

[0026] The output of the electric motor 21 is reduced by the reduction mechanism 3 and then transmitted to the rack shaft 12 via the output shaft 15 as steering assist torque.

[0027] The torque sensor 40 detects the steering torque applied to the torsion bar 14 based on the difference in rotational angles between the input shaft 13 and the output shaft 15.

[0028] The circuit board 47 of the torque sensor 40 (see Figure 5) and the controller 30 are electrically connected via a cable 36 that serves as a signal line. Through the cable 36, power is supplied from the controller 30 to the torque sensor 40, and the steering torque signal detected by the torque sensor 40 is output to the controller 30.

[0029] Next, with reference to Figures 2-5, the structure of the assist mechanism 20 in the electric power steering system 100 will be described in detail.

[0030] As shown in Figures 2 and 3, the assist mechanism 20 comprises an electric motor 21, a housing 5, an input shaft 13, a torsion bar 14, an output shaft 15, and a torque sensor 40. The input shaft 13, the output shaft 15, and the torque sensor 40 are housed in the housing 5.

[0031] As shown in Figures 2 and 3, the housing 5 includes a first housing 50 and a second housing 60.

[0032] As shown in Figures 2 and 3, the first housing 50 has a cylindrical portion 51, a flange portion 52 extending radially outward from the outer circumference of the cylindrical portion 51 and covering the opening of the second housing 60, and a mounting portion 53 into which a bolt 18 for fastening the first housing 50 and the second housing 60 is inserted.

[0033] As shown in Figure 3, the cylindrical portion 51 is provided with a sealing member 91 that slides against the outer surface of the input shaft 13 and a bearing 92 that rotatably supports the input shaft 13. The sealing member 91 prevents foreign matter from entering the first housing 50.

[0034] As shown in Figures 2 and 3, the mounting portion 53 is formed to protrude radially outward from the outer circumferential surface of the flange portion 52. In this embodiment, three mounting portions 53 are provided at intervals in the circumferential direction.

[0035] As shown in Figures 2 to 4, the second housing 60 includes a first cylindrical portion 61, a second cylindrical portion 62 having a smaller inner diameter than the first cylindrical portion 61, a mounting portion 63 into which bolts 18 for fastening the first housing 50 and the second housing 60 are inserted, a holder mounting portion 66 (see Figure 4) to which a cable holder 31 for holding the cable 36 is attached, and a plate 69 provided inside the first cylindrical portion 61.

[0036] As shown in Figure 2, an electric motor 21 is mounted on the outer wall surface of the first cylindrical portion 61. As shown in Figure 3, a torque sensor 40 and a worm wheel 3b are housed inside the first cylindrical portion 61. The worm shaft 3a, connected to the output shaft 22 of the electric motor 21, is positioned to pass through the first cylindrical portion 61 and meshes with the worm wheel 3b housed inside the first cylindrical portion 61. As shown in Figure 3, the inside of the first cylindrical portion 61 is divided by a disc-shaped plate 69 into a space where the torque sensor 40 is provided and a space where the worm wheel 3b is provided.

[0037] As shown in Figure 4, the first cylindrical portion 61 has a through hole 61a formed to penetrate the first cylindrical portion 61. A cable 36 is inserted through the through hole 61a.

[0038] As shown in Figure 3, the second cylindrical portion 62 is provided with a bearing 93 that rotatably supports the output shaft 15 and a sealing member 94 that slides against the outer circumferential surface of the output shaft 15. The sealing member 94 prevents foreign matter from entering the second housing 60.

[0039] As shown in Figures 2 and 3, the first housing 50 and the second housing 60 are fastened together by bolts 18. An annular O-ring 96 is provided between the first housing 50 and the second housing 60 to seal the space between them.

[0040] As shown in Figure 3, a hollow section is formed in the axis of the input shaft 13, opening at its lower end face, and a torsion bar 14 is housed within this hollow section. The upper side of the torsion bar 14 is connected to the input shaft 13 by a pin 17. The lower end of the torsion bar 14 protrudes from the lower end opening of the hollow section of the input shaft 13 and is connected to the output shaft 15 via serrations 14a. The torsion bar 14 transmits the steering torque input to the input shaft 13 via the steering wheel 1 to the output shaft 15, and twists and deforms around its axis in accordance with the steering torque. In this way, the input shaft 13 and the output shaft 15 rotate relative to each other according to the amount of twist of the torsion bar 14, and the torque sensor 40 detects the steering torque based on the difference in rotational angles between the input shaft 13 and the output shaft 15 due to this relative rotation.

[0041] Next, the specific structure of the torque sensor 40 will be described with reference to Figures 3 to 5. Figure 5 is an enlarged view of the area R enclosed by a circle in Figure 3.

[0042] As shown in Figures 3 and 5, the torque sensor 40 includes a case 41, a first sensor rotor 45 which rotates integrally with the input shaft 13, a second sensor rotor 46 which rotates integrally with the output shaft 15, a circuit board 47 which detects steering torque and outputs the signal to the controller 30, and a connector 49 to which the cable 36 (see Figures 3 and 4) is connected.

[0043] As shown in Figure 4 and other figures, the case 41 has a substantially annular shape through which the input shaft 13 is inserted, and is provided to be rotatable relative to the input shaft 13.

[0044] The case 41 is formed from a resin material. As shown in Figures 4 and 5, the case 41 has a cylindrical first cylindrical portion 41a, a cylindrical second cylindrical portion 41b which is larger in diameter than the first cylindrical portion 41a, an annular projection 41c projecting radially inward from the inner circumferential surface of the first cylindrical portion 41a, a bulge 41d formed to bulge radially outward from the outer circumferential surface of the first cylindrical portion 41a, and an engaging portion 48 formed to further project radially from the outer surface of the bulge 41d. In this embodiment, the projection 41c is formed to taper radially inward.

[0045] As shown in Figure 4, the engaging portion 48 engages with a locking portion 68 formed on the plate 69. A pair of locking portions 68 are provided spaced apart in the rotational direction of the input shaft 13, extending axially from the end face of the plate 69. A leaf spring 80 is provided between one end face of the engaging portion 48 and the locking portion 68 in the rotational direction. The engagement portion 48 is pressed against one of the locking portions 68 by the elastic force of the leaf spring 80, thereby restricting the relative rotation of the torque sensor 40 (case 41) with respect to the housing 5.

[0046] As shown in Figure 5, the first sensor rotor 45 has a first rotor member 45a that is press-fitted onto the outer circumferential surface of the input shaft 13, and a plurality of plate portions 45b that are attached to the lower end surface of the first rotor member 45a so as to face the substrate 47 and are formed to extend radially in the radial direction. The first rotor member 45a is made of a resin material. The plurality of plate portions 45b are arranged at predetermined intervals in the rotational direction. The first rotor member 45a and the plurality of plate portions 45b are integrated by insert molding to form the first sensor rotor 45.

[0047] As shown in Figure 5, an annular engagement groove 45c is provided on the outer circumferential surface of the first rotor member 45a, into which the projection 41c of the case 41 engages. The engagement groove 45c is shaped such that its side surface is in surface contact with the side surface of the projection 41c; specifically, the side surface of the engagement groove 45c is formed such that its width narrows towards the bottom surface.

[0048] In the torque sensor 40 of this embodiment, the case 41 is supported in a so-called floating state, rotatable relative to the input shaft 13 via the first rotor member 45a, by the engagement of the projection 41c with the engagement groove 45c. As a result, the plate portion 45b of the first sensor rotor 45 rotates relative to the substrate 47 as the input shaft 13 rotates. Furthermore, the engagement of the projection 41c and the engagement groove 45c, which are formed in the shape described above, restricts the axial and radial movement of the case 41 of the input shaft 13.

[0049] As shown in Figure 5, the second sensor rotor 46 has a press-fit portion 46a that is press-fitted onto the outer circumferential surface of the output shaft 15, and a plurality of plate portions 46b that are formed extending radially from the outer circumferential surface of the press-fit portion 46a and are arranged to face the substrate 47 at predetermined intervals in the rotational direction.

[0050] The substrate 47 is fixed inside the case 41 and is positioned between the plate portion 45b of the first sensor rotor 45 and the plate portion 46b of the second sensor rotor 46. A detection coil pattern is formed on the substrate 47 by patterning. The detection coil pattern detects the steering torque by detecting the change in the magnetic field associated with the difference in rotation angle between the input shaft 13 and the output shaft 15, that is, the difference in rotation angle between the first sensor rotor 45 and the second sensor rotor 46. In this way, the torque sensor 40 is an inductance type sensor that detects the steering torque based on the change in inductance detected by the detection coil pattern.

[0051] As shown in Figures 3 and 4, the connector 49 is positioned on the top surface of the case 41 and is held in place by the case 41. The connector 49 is a female connector having a mounting opening 49a. A male connector 37 (see Figure 4) provided at the end of the cable 36 is inserted into the mounting opening 49a.

[0052] One end of the cable 36 is connected to the connector 37 (torque sensor 40). The cable 36 is routed out of the housing 5 through the through hole 61a formed in the first cylindrical portion 61, the holder mounting portion 66, and the cable holder 31. The other end of the cable 36 is connected to the controller 30. Note that it is not necessary to connect the torque sensor 40 and the controller 30 with a single cable 36. For example, a relay connector may be provided in the cable holder 31 or the through hole 61a, and the cable 36 inside the housing 5 and the cable 36 outside the housing 5 may be connected by the relay connector.

[0053] Incidentally, when guiding the cable 36 from the outside to the inside of the housing 5, it is conceivable to provide a through-hole in the housing 5 that extends radially toward the center of the housing 5 (the rotation axis of the input shaft 13), and insert the cable 36 through this through-hole (the area indicated by P in Figure 4). However, in such a configuration, once the cable 36 is inserted through the through-hole, the cable 36 is guided into the housing 5 so as to face the input shaft 13 and the case 41, and is bent inside the housing 5 to bypass the input shaft 13 and the case 41 (see the dotted line in Figure 4). When the cable 36 is bent in this way and connected to the connector 49, the restoring force of the cable 36 may put a load on the connector 49 and the case 41 of the torque sensor 40 that holds the connector 49, which may have adverse effects. Specifically, when a load is placed on the connector 49, the case 41 that holds the connector 49 may rotate while being pressed against the first rotor member 45a. Furthermore, when the first rotor member 45a rotates while the case 41 is pressed against it, the contact portion between the engagement groove 45c of the first rotor member 45a and the protrusion 41c of the case 41 wears down. As a result, the substrate 47 held by the case 41 becomes loose, which may worsen the detection accuracy of the torque sensor 40.

[0054] Therefore, as shown in Figure 4, in the electric power steering device 100 of this embodiment, the through hole 61a is provided at a position offset parallel to the position P where the axis is directed toward the center of the housing 5 (the rotation axis of the input shaft 13). In other words, the through hole 61a is provided such that its axis is inclined with respect to the direction toward the center of the housing 5 (the rotation axis of the input shaft 13) on a plane perpendicular to the rotation axis of the input shaft 13, that is, the opening of the through hole 61a is not directed toward the case 41 of the torque sensor 40 or the input shaft 13.

[0055] By providing the through-hole 61a in this way, it is not necessary to bend the cable 36 inserted through the through-hole 61a in order to bypass the case 41 of the torque sensor 40 or the input shaft 13. In other words, the cable 36 inserted through the through-hole 61a can be guided linearly along the inner surface of the housing 5 (hereinafter, the portion of the cable 36 that extends linearly along the inner surface of the housing 5 will be referred to as the "relaxation portion 36a").

[0056] The cable 36 is bent at the point where it connects the connector 49 to the relaxation section 36a (hereinafter, the bent portion of the cable 36 where it connects the connector 49 to the relaxation section 36a will be referred to as the "bent section 36b"). At the bent section 36b, a restoring force acts on the cable 36, causing it to return to a straight state. On the other hand, no restoring force is generated at the relaxation section 36a; conversely, the relaxation section 36a can absorb the load caused by the restoring force of the cable 36 generated at other parts of the cable 36 (such as the bent section 36b). Therefore, by providing a relaxation section 36a on the cable 36, the load caused by the restoring force of the cable 36 acting on the connector 49 and the case 41 of the torque sensor 40 that holds the connector 49 can be reduced.

[0057] Furthermore, in the electric power steering device 100 of this embodiment, as shown in Figure 4, the connector 49 is provided in the region opposite to the through-hole 61a on the other side of the input shaft 13, specifically, in the region opposite to the through-hole 61a on the other side of the plane F that is perpendicular to the relaxation portion 36a (axis D2 of the through-hole 61a) within the plane including the rotation axis of the input shaft 13. By providing the connector 49 in the region opposite to the through-hole 61a on the other side of the input shaft 13 in this way, the length of the cable 36 inside the housing 5 can be increased. As a result, even if the cable 36 is bent, the longer the cable 36, the more slack there is in the cable 36, which can alleviate the load caused by the restoring force of the cable 36.

[0058] Furthermore, it is desirable that the angle θ between the connection direction D1 between the connector 49 and the cable 36 and the axis D2 of the through hole 61a be approximately 90°. For example, if the angle θ between the connection direction D1 between the connector 49 and the cable 36 and the axis D2 of the through hole 61a is less than 90° (see Figure 6; in Figure 6, the angle θ is approximately 0°), the cable 36 may lose its elasticity due to aging or other factors, and the portion of the cable 36 between the connector 49 and the through hole 61a may deform linearly in an attempt to connect them at the shortest distance (see the thick dotted line in Figure 6). If the cable 36 deforms linearly in this way, it may come into contact with the case 41 or input shaft 13 of the torque sensor 40, potentially causing adverse effects. Conversely, if the angle θ is greater than 90°, the length of the cable 36 will be shortened, and the amount of play will be reduced accordingly. Therefore, by setting the angle θ to approximately 90°, even if the cable 36 deforms linearly, it is possible to suppress contact between the cable 36 and the case 41 of the torque sensor 40 or the input shaft 13, while also ensuring maximum play in the cable 36.

[0059] Furthermore, it is desirable that the connector 49 and the through-hole 61a are located on the same plane perpendicular to the rotation axis of the input shaft 13. By providing the connector 49 and the through-hole 61a on the same plane in this way, the portion of the cable 36 that is bent in the direction of the rotation axis of the input shaft 13 can be eliminated.

[0060] Furthermore, the cable 36 may be fixed to the housing 5 (plate 69) by a fixing member (not shown) in the intermediate portion between the connector 49 and the through hole 61a. By fixing the cable 36 to the housing 5 (plate 69) in this way, the load acting on the connector 49 and the case 41 of the torque sensor 40 that holds the connector 49 can be reduced. In particular, it is preferable to fix the bent portion 36b to the housing 5 with a fixing member. By fixing the bent portion 36b, the restoring force that causes the bent portion 36b to return to a straight state can be suppressed by the fixing member, so the load acting on the connector 49 and the case 41 of the torque sensor 40 that holds the connector 49 can be further reduced.

[0061] The configuration, operation, and effects of the embodiments of the present invention will be described below.

[0062] The electric power steering device 100 includes an input shaft 13 to which steering torque is input, an output shaft 15 connected to the input shaft 13 via a torsion bar 14, a torque sensor 40 mounted across the input shaft 13 and the output shaft 15 for detecting steering torque, a housing 5 housing the input shaft 13, the output shaft 15, and the torque sensor 40, an electric motor 21 that generates steering assist torque based on the detection result of the torque sensor 40, a connector 49 held in the case 41 of the torque sensor 40 and electrically connected to the torque sensor 40, a through hole 61a formed to penetrate the outer wall of the housing 5, and a cable 36 inserted through the through hole 61a for electrically connecting the connector 49 to external equipment, wherein the cable 36 has a relaxation portion 36a that extends linearly from the through hole 61a along the inner surface of the housing 5.

[0063] In this configuration, the cable 36 has a relaxation portion 36a that extends linearly from the through hole 61a along the inner surface of the housing 5. This eliminates the need to bend the cable 36 to avoid the input shaft 13, thus reducing the amount of bending required for the cable 36. Consequently, the load on the connector 49 and the case 41 of the torque sensor 40 that holds the connector 49 due to the restoring force of the cable 36 can be reduced.

[0064] Furthermore, in the electric power steering device 100, the connector 49 is provided in the area opposite to the through hole 61a, with the input shaft 13 in between, and the angle θ between the connection direction D1 between the connector 49 and the cable 36 and the axis D2 of the through hole 61a is approximately 90°.

[0065] In this configuration, the connector 49 is located in the area opposite the through-hole 61a, with the input shaft 13 in between, which allows for a longer cable length within the housing 5. This means that even if the cable 36 is bent, the longer length of the cable 36 creates some slack, thus mitigating the load caused by the restoring force of the cable 36. Furthermore, since the angle θ between the connection direction D1 between the connector 49 and the cable 36 and the axis D2 of the through-hole 61a is approximately 90°, the amount of bending of the cable 36 can be minimized, and the length of the mitigation section 36a can be maximized. For example, if the angle θ between the connection direction D1 between the connector 49 and the cable 36 and the axis D2 of the through-hole 61a is greater than 90° (see Figure 6), there is a risk that the cable 36 may deform linearly in an attempt to connect the connector 49 and the through-hole 61a at the shortest distance if the cable 36 loses its elasticity due to aging or other factors (see the thick dotted line in Figure 6). As described above, if the cable 36 deforms linearly, it may come into contact with the case 41 or input shaft 13 of the torque sensor 40, potentially causing adverse effects. Therefore, by setting the angle θ to approximately 90°, even if the cable 36 deforms linearly, contact between the cable 36 and the case 41 or input shaft 13 of the torque sensor 40 can be suppressed. Furthermore, by maximizing the length of the mitigation section 36a, the area in which the load due to the restoring force of the cable 36 is mitigated can be enlarged.

[0066] In the electric power steering device 100, the connector 49 and the through-hole 61a are located on the same plane perpendicular to the rotation axis of the input shaft 13.

[0067] In this configuration, by placing the connector 49 and the through-hole 61a on the same plane, the bending portion of the cable 36 in the direction of the rotation axis of the input shaft 13 can be eliminated.

[0068] The electric power steering device 100 further includes a fixing member for fixing the cable 36 to the housing 5, the cable 36 further has a bent portion 36b that connects the connector 49 and the relaxation portion 36a, and the fixing member fixes the bent portion 36b to the housing 5.

[0069] In this configuration, the bent portion 36b of the cable 36 is fixed to the housing 5, which reduces the load acting on the connector 49 and the case 41 of the torque sensor 40 that holds the connector 49.

[0070] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0071] The torque sensor 40 may also be configured to function as an angle sensor that detects the absolute rotation angle of the steering shaft 11.

[0072] In the above embodiment, a single-pinion type electric power steering system 100 was described as an example in which the steering torque from the driver and the steering assist torque from the electric motor 21 are input to the rack shaft 12 via a common steering shaft 11. However, the electric power steering system 100 may also be a dual-pinion type electric power steering system in which the steering torque from the driver and the steering assist torque from the electric motor 21 are independently input to the rack shaft 12. Furthermore, the electric power steering system 100 is not limited to a rack and pinion system, but may also be a column-assist type.

[0073] In the above embodiment, the case where the torque sensor 40 is an inductance type sensor was described. However, the torque sensor 40 may also be a magnetic type sensor, and the torque detection method is not limited. [Explanation of Symbols]

[0074] 1...Steering wheel, 3...Reduction mechanism, 3a...Worm shaft, 3b...Worm wheel, 5...Housing, 10...Steering mechanism, 13...Input shaft, 14...Torsion bar, 15...Output shaft, 16...Pinion, 20...Assist mechanism, 21...Electric motor, 22...Output shaft, 30...Controller, 36...Cable, 36a... Relaxation section, 37... Connector, 40... Torque sensor, 41... Case, 45... First sensor rotor, 46... Second sensor rotor, 47... Circuit board, 48... Engaging section, 49... Connector, 50... First housing, 60... Second housing, 61a... Through hole, 69... Plate (housing), 100... Electric power steering device, D1... Connection direction, D2... Axis

Claims

1. An electric power steering system, The input shaft to which steering torque is input, An output shaft connected to the input shaft via a torsion bar, A torque sensor is mounted across the input shaft and the output shaft to detect the steering torque, A housing that accommodates the input shaft, the output shaft, and the torque sensor, Based on the detection results of the torque sensor, an electric motor is used to generate steering assist torque, A connector is held in the case of the torque sensor and electrically connected to the torque sensor, A through hole formed so as to penetrate the outer wall of the housing, The device comprises a cable inserted through the through-hole and electrically connecting an external device to the connector, The cable has a relaxation portion that extends linearly in close proximity to the inner circumferential surface of the cylindrical portion of the housing in which the through hole is formed, The connector is provided in the region opposite to the through-hole, with the input shaft in between. An electric power steering device characterized in that the angle between the connection direction of the connector and the cable and the axis of the through hole is approximately 90°.

2. An electric power steering device according to Claim 1, An electric power steering device characterized in that the connector and the through hole are located on the same plane perpendicular to the rotation axis of the input shaft.

3. An electric power steering device, The input shaft to which steering torque is input, An output shaft connected to the input shaft via a torsion bar, A torque sensor is mounted across the input shaft and the output shaft to detect the steering torque, A housing that accommodates the input shaft, the output shaft, and the torque sensor, Based on the detection results of the torque sensor, an electric motor is used to generate steering assist torque, A connector is held in the case of the torque sensor and electrically connected to the torque sensor, A through hole formed so as to penetrate the outer wall of the housing, A cable inserted through the aforementioned through hole and electrically connecting the external equipment and the connector, The system includes a fixing member for fixing the cable to the housing, The cable has a relaxation portion that extends linearly in close proximity to the inner circumferential surface of the cylindrical portion of the housing in which the through hole is formed, The cable further has a bent portion that connects the connector and the relaxation portion, The aforementioned fixing member is characterized by fixing the bent portion to the housing.

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