Electric power steering device

Abstract

The housing of this power steering device comprises two or more partial housings and two or more bolts. The partial housings have a fastening surface in contact with another partial housing. The two or more partial housings include a first partial housing and a second partial housing. The first partial housing has a first fastening surface and two or more first flanges having formed therein a hole into which the shaft parts of the bolts are inserted. The second partial housing has a second fastening surface facing the first fastening surface, and two or more second flanges having formed therein a hole into which the shaft parts of the bolts are inserted. One of the first fastening surface and the second fastening surface is provided with at least one protruding section protruding toward the other fastening surface, and the protruding section is arranged so as to be offset from the first flange in the circumferential direction around the center of the first fastening surface.

Description

Electric power steering device

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

[0002] One example of a steering device is an electric power steering device that assists the driver's steering force, as disclosed in the following patent document. This electric power steering device includes a steering column to which a steering wheel is attached, an input shaft connected to the steering column, an output shaft arranged coaxially with the input shaft, a torsion bar connecting the input shaft and the output shaft, a torque sensor that detects the amount of torsion (amount of relative rotation) of the torsion bar, a motor that generates an assist force, a reduction gear that reduces the torque generated by the motor and transmits it to the output shaft, and a housing that accommodates the above-mentioned components. The housing mainly includes a housing (sometimes referred to as a column housing) that mainly accommodates the steering shaft, and a gearbox that mainly accommodates the output shaft, torque sensor, reduction gear, and motor. Hereinafter, divided parts of the housing, such as the housing and the gearbox, will be referred to as partial housings.

[0003] Japanese Patent Application Laid-Open No. 2018-204755

[0004] Incidentally, partial housings are connected to each other by fastening bolts. Hereinafter, the surface of one partial housing that comes into contact with another partial housing will be referred to as the fastening surface. This fastening surface is formed in an annular shape, but when the bolt is fastened, there is a possibility that the entire fastening surface (entire circumference) will not come into contact with the other fastening surface. In other words, the portion of the fastening surface to which the axial force is applied will come into contact with the opposing fastening surface. On the other hand, the portion of the fastening surface to which the axial force is not applied will not come into contact with the opposing fastening surface, and a gap may occur. As a result, this gap changes the natural frequency of the partial housing. If the changed natural frequency of the partial housing matches the vibration of the order component relative to the rotation of the motor rotor, noise may be generated from the partial housing.

[0005] The present disclosure has been made in view of the above, and has an object to provide a power steering device that is less likely to generate noise.

[0006] In order to achieve the above object, an electric power steering device according to one aspect of the present disclosure includes a housing. The housing includes at least two or more partial housings and two or more bolts that fasten the partial housings together. The partial housings have fastening surfaces that come into contact with other partial housings when the bolts are fastened. The two or more partial housings include a first partial housing and a second partial housing. The first partial housing has a first fastening surface that is the fastening surface and two or more first flanges that are arranged on the outer periphery of the first fastening surface and have holes into which shanks of the bolts are inserted. The second partial housing has a second fastening surface that is the fastening surface and faces the first fastening surface, and two or more second flanges that are arranged on the outer periphery of the second fastening surface and have holes into which shanks of the bolts are inserted and face the first flanges. One of the first fastening surface and the second fastening surface has at least one protrusion that protrudes toward the other of the first fastening surface and the second fastening surface. The protrusion is disposed with respect to the first flange so as to be shifted in the circumferential direction about the center of the first fastening surface.

[0007] Axial force acts on the fastening surface in the axial direction of the bolt, but axial force is less likely to act on the fastening surface in the portion offset from the axial direction of the bolt. According to the present disclosure, the convex portion is positioned offset circumferentially from the axial direction of the first flange (bolt), so that even the portion where axial force is less likely to act reliably contacts the opposing fastening surface. This avoids changes in the natural frequency of the partial housing and suppresses noise generation.

[0008] The housing of the electric power steering device may house a steering shaft, an input shaft, a torsion bar, an output shaft, a torque sensor, a motor, and a reduction gear.

[0009] In addition, the number of bolts in the electric power steering device may be two, the number of first flanges may be two, the two first flanges may be arranged point-symmetrically around the center of the first fastening surface, and the number of second flanges may be two.

[0010] Furthermore, in the above-described electric power steering device, it is preferable that, when viewed from a direction perpendicular to the first fastening surface, the angle formed by a first imaginary line drawn from the center of the first fastening surface to the first flange and a second imaginary line drawn from the center of the first fastening surface to the convex portion is 90°.

[0011] The convex portion is formed in the portion of the fastening surface where axial force is least likely to act, i.e., in the direction of the first imaginary line that forms a 90° angle with the second imaginary line drawn from the center of the first fastening surface to the first flange. This ensures that the fastening surface contacts the opposing fastening surface. As a result, changes in the natural frequency of the partial housing are avoided, and noise generation is suppressed.

[0012] In addition, the convex portion of the electric power steering device is a pair of partial convex portions spaced apart from each other in the circumferential direction, and when viewed from a direction perpendicular to the first fastening surface, an angle formed by a first imaginary line drawn from the center of the first fastening surface to the first flange and a third imaginary line drawn from the center of the first fastening surface between the pair of partial convex portions is 90°.

[0013] The protrusions are formed on the fastening surfaces where axial force is least likely to act, ensuring reliable contact with the opposing fastening surfaces. This prevents changes in the natural frequency of the partial housing and suppresses noise generation.

[0014] In a preferred embodiment of the electric power steering device, two protrusions are provided, and the two protrusions are arranged point-symmetrically with respect to the center of the first fastening surface.

[0015] According to the above-mentioned configuration, the gap between the fastening surfaces is further reduced, which reliably prevents a change in the natural frequency of the partial housing and suppresses the generation of noise.

[0016] In the electric power steering device, the length of the convex portion extending in the circumferential direction along the fastening surface may be gradually reduced from the base of the convex portion toward the tip of the convex portion.

[0017] In the electric power steering device, the first partial housing may be a gear box that houses at least the reduction gear device, and the second partial housing may be a housing.

[0018] In the electric power steering device, the first partial housing may be a gear box that houses at least the reduction gear transmission, and the second partial housing may be a motor housing that supports the motor.

[0019] In the electric power steering device described above, the two or more partial housings include a third partial housing arranged in a direction opposite to the first partial housing when viewed from the second partial housing. The second partial housing has a third fastening surface arranged on a rear side of the second fastening surface. The third partial housing has a fourth fastening surface that is the fastening surface and faces the third fastening surface, and two third flanges that are arranged on the outer circumferential side of the fourth fastening surface, have through holes into which the shanks of the bolts are inserted, and face the second flanges. One of the third fastening surface and the fourth fastening surface is provided with at least one or more convex portions that protrude toward the other of the third fastening surface and the fourth fastening surface. When viewed from a direction perpendicular to the first fastening surface, the convex portion provided on the first fastening surface or the second fastening surface may overlap the convex portion provided on the third fastening surface or the fourth fastening surface.

[0020] In addition, the first partial housing of the electric power steering device may be a gear box that accommodates at least the reduction gear device, the second partial housing may be an annular intermediate plate, and the third partial housing may be a housing.

[0021] Furthermore, the convex portion of the electric power steering device may be formed as a separate part from the partial housing.

[0022] The power steering device according to the present disclosure is less likely to produce noise.

[0023] FIG. 1 is a schematic diagram of a steering device according to a first embodiment. FIG. 2 is a perspective view of a housing of the power steering device according to the first embodiment. FIG. 3 is an exploded perspective view of the gearbox, intermediate plate, and housing of the first embodiment. FIG. 4 is a cross-sectional view of the bracket of the power steering device according to the first embodiment cut in the vertical and horizontal directions. FIG. 5 is a view of the gearbox according to the first embodiment as seen from the intermediate plate side. FIG. 6 is a cross-sectional view taken along the arrow VI-VI in FIG. 5. FIG. 7 is a cross-sectional view of the housing according to the first embodiment cut along the same line as the cross-sectional view of FIG. 6. FIG. 8 is a cross-sectional view of a convex portion of a first modification cut in the circumferential direction. FIG. 9 is a cross-sectional view of a convex portion of a second modification cut in the circumferential direction. FIG. 10 is a view of a convex portion of a third modification cut in the axial direction.

[0024] The present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the following modes for carrying out the invention (hereinafter referred to as embodiments). Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0025] (Embodiment 1) Fig. 1 is a schematic diagram of a steering device according to embodiment 1. As shown in Fig. 1, an electric power steering device 100 includes a steering wheel 81, a steering shaft 82, a universal joint 83, an intermediate shaft 84, a universal joint 85, a pinion 86, a rack bar 87, and a tie rod 88, which are connected in this order.

[0026] The steering shaft 82 is rotated by the driver's force. The rotational motion of the steering shaft 82 is transmitted in turn to the pinion shaft 104, causing it to rotate. A pinion gear 105a is provided on the pinion 86, and is engaged with the rack of the rack bar 87. This converts the rotational motion of the pinion 86 into linear motion by the rack bar 87. The linear motion of the rack bar 87 moves the tie rod 88 left and right, changing the angle of the wheels.

[0027] Furthermore, in order to assist the force of the driver, the electric power steering device 100 has an input shaft 82a (see FIG. 4) connected to the steering shaft 82, an output shaft 89 connected to the universal joint 83, and a torsion bar (not shown) that connects the input shaft 82a and the output shaft 89. In addition, the electric power steering device 100 has a torque sensor 90, a motor 91, a reduction gear 92, and a control device 93 that controls the operation of the motor 91.

[0028] The torque sensor 90 detects the amount of twist (amount of relative rotation) of the torsion bar, and sends the detection result to the control device 93. The control device 93 issues a drive command to the motor 91 so as to eliminate the twist of the torsion bar.

[0029] The motor 91 receives a drive command and generates torque. The torque generated by the motor 91 is reduced in speed by the reduction gear 92 and transmitted to the output shaft 89. This causes the output shaft 89 to rotate, eliminating twisting of the torsion bar. The torque transmitted to the output shaft 89 is also transmitted to the pinion 86 and rack bar 87, changing the angle of the wheels. As a result, the force required by the driver to operate the steering wheel 81 is reduced.

[0030] The electric power steering device 100 has a housing 1 attached to the front of the vehicle body. The housing 1 accommodates a steering shaft 82, an input shaft 82a, a torsion bar, an output shaft 89, a torque sensor 90, a motor 91, a reduction gear 92, and a control device 93. The housing 1 will be described in detail below.

[0031] FIG. 2 is a perspective view of the housing of the power steering device of the first embodiment. FIG. 3 is an exploded perspective view of the gearbox, intermediate plate, and housing of the first embodiment. FIG. 4 is a cross-sectional view of the bracket of the power steering device of the first embodiment cut in the vertical and horizontal directions. The housing 1 includes a housing 10, an intermediate plate 20, a gearbox 30, and a motor housing 40. The housing 10, the intermediate plate 20, and the gearbox 30 are fastened together by two first bolts 51. The gearbox 30 and the motor housing 40 are fastened together by two second bolts 52. Hereinafter, the housing 10, the intermediate plate 20, the gearbox 30, and the motor housing 40 that constitute the housing 1 may each be referred to as a partial housing.

[0032] Next, the partial housing will be described in detail. When describing directions, the direction parallel to the central axis O1 of the steering shaft 82 will be referred to as the axial direction. Furthermore, when viewed from the housing 10, the direction in which the gearbox 30 is disposed will be referred to as the first axial direction X1, and the opposite direction will be referred to as the second axial direction X2.

[0033] As shown in Figures 2 and 3, the housing 10 has a cylindrical main body 11 and a disk-shaped cover 12 provided at the end of the main body 11 in the first axial direction X1. A cylindrical steering column 2 is inserted into the main body 11. The steering column 2 rotatably supports a steering shaft 82. The main body 11 supports the steering column 2 so that it can move (slide) in the axial direction. Therefore, by moving the steering column 2 in the axial direction, the position of the steering wheel 81 can be changed in the axial direction.

[0034] The end of the main body 11 in the second axial direction X2 is supported by a bracket 3 attached to the vehicle body. Specifically, as shown in FIG. 4 , the main body 11 is disposed between a pair of vertical walls 3 a, 3 b of the bracket 3. When the lever 4 of the bracket 3 is rotated, the shaft 4 a connected to the lever 4 rotates, and a clamping force (see arrow B in FIG. 4 ) acts on the main body 11 from the pair of vertical walls 3 a, 3 b. The clamping force is parallel to the rotation center O2 of the lever 4 (a direction perpendicular to the axial direction). Hereinafter, the direction parallel to the rotation center O2 of the lever 4 (shaft 4 a) will be referred to as the left-right direction Y. Furthermore, the direction perpendicular to both the axial direction and the left-right direction Y will be referred to as the up-down direction Z.

[0035] The main body 11 has a slit 11a extending in the axial direction. The slit 11a is located downward when viewed from the central axis O1. When a tightening force is applied to the main body 11, the width of the slit 11a in the main body 11 decreases. In other words, the inner diameter of the main body 11 decreases, and the main body 11 tightens the steering column 2. This fixes the axial position of the steering column 2 (steering wheel).

[0036] The cover 12 is a lid that closes the gearbox 30 from the second axial direction X2. As shown in Fig. 3, two first flanges 13 that protrude radially outward are provided on the outer peripheral surface of the cover 12. These two first flanges 13 are arranged in the up-down direction Z when viewed from the central axis O1. Each first flange 13 has a hole that penetrates in the axial direction.

[0037] The intermediate plate 20 is cylindrical and has a short axial length. The intermediate plate 20 is disposed between the cover 12 and the gearbox 30. A partition wall 21 extending in a direction perpendicular to the central axis O1 is formed on the inner peripheral surface of the intermediate plate 20. A torque sensor is disposed in the internal space formed between the cover 12 and the intermediate plate 20.

[0038] The partition wall 21 has a hole 22 formed therethrough in the axial direction. Two second flanges 23 that protrude radially outward are formed on the outer peripheral surface of the intermediate plate 20. The second flanges 23 are arranged at 180° intervals. In other words, the two second flanges 23 are arranged point-symmetrically about the central axis O1. The second flanges 23 also have a hole 23a formed therethrough in the axial direction.

[0039] FIG. 5 is a view of the gearbox of the first embodiment as viewed from the intermediate plate side. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. As shown in FIG. 5, the gearbox 30 includes a first main body portion 31 having a bottom and a cylindrical shape centered on a central axis O1, and a second main body portion 32 provided on a side of the first main body portion 31 in the left-right direction Y. The first main body portion 31 opens toward the second axial direction X2 (the intermediate plate) and is closed by the cover 12 via the intermediate plate 20. Two third flanges 35 protruding radially outward are provided on the outer peripheral surface of the first main body portion 31. The third flanges 35 are arranged at 180° intervals. That is, the two third flanges 35 are arranged point-symmetrically about the central axis O1. The third flanges 35 also include a hole 35a that opens toward the second axial direction X2. A thread groove (not shown) is formed on the inner peripheral surface of the hole 35a.

[0040] A hole 34 is formed in the bottom 33 of the first main body portion 31, penetrating in the axial direction. As shown in FIG. 3 , the hole 34 of the gearbox 30 and the hole 23a of the intermediate plate 20 are arranged on the central axis O1. In other words, the housing 1 is provided with a hole (space) extending along the central axis O1. The steering shaft 82, the input shaft, the torsion bar, and the output shaft 89 are arranged in this extending hole (space) in this order from the second axial direction X2.

[0041] As shown in Fig. 5, the second main body portion 32 has a cylindrical portion 36 that extends tangentially to the outer circumferential surface of the first main body portion 31, and a disk portion 37 provided at one end of the cylindrical portion 36. As shown in Fig. 3, two fourth flanges 38 that protrude radially outward are provided on the outer circumferential surface of the disk portion 37. A hole 38a is formed in each of the fourth flanges 38. A thread groove (not shown) is formed on the inner circumferential surface of the hole 38a.

[0042] The disk portion 37 is a seating surface on which a motor 91 is mounted. An output shaft (see central axis O3 in FIGS. 3 and 5 ) of the motor mounted on the disk portion 37 is disposed in the cylindrical portion 36. The interior of the cylindrical portion 36 is connected to the interior of the first main body portion 31. A reduction gear 92 is disposed in the cylindrical portion 36 and the first main body portion 31. The reduction gear 92 is not particularly limited, but examples thereof include a worm disposed in the cylindrical portion 36 and a worm gear disposed inside the first main body portion 31. The two fourth flanges 38 are disposed point-symmetrically about the central axis O3.

[0043] The motor housing 40 is a cylindrical part to which a stator is fixed on the inner circumferential surface, and is sometimes referred to as a motor case. In other words, the motor housing 40 is one component of the motor. In this embodiment, a control device 93 is integrated with the motor 91. The integrated control device 93 and motor 91 may be referred to as a motor control unit (hereinafter referred to as MCU 94).

[0044] Two fifth flanges 41 protruding radially outward are provided on the outer peripheral surface of the motor housing 40. The two fifth flanges 41 face the fourth flanges 38 of the gearbox 30 and are arranged at an interval of 180°.

[0045] When assembling the housing 1 of the electric power steering device 100, the gearbox 30, the intermediate plate 20, and the housing 10 are arranged in this order from the first axial direction X1. Then, the first flange 13, the second flange 23, and the third flange 35 are aligned so that they face the up-down direction Z. The shanks of the first bolts 51 are inserted into the first flange 13 and the second flange 23 from the second axial direction X2 and screwed into the holes 35a of the third flange 35. This tightens the heads of the first bolts 51, integrating the housing 10, the intermediate plate 20, and the gearbox 30.

[0046] Additionally, the second main body 32 and the MCU 94 are positioned along the central axis O3. The fourth flange 38 and the fifth flange 41 are aligned so that they face each other. Then, the shank of the second bolt 52 is inserted into the through-hole 51a of the fifth flange 41 and screwed into the hole 38a of the fourth flange 38. This integrates the gearbox 30 and the MCU 94 (motor housing 40).

[0047] Each partial housing also has a surface that comes into contact with another partial housing when bolted. The first main body portion 31 of the gearbox 30 has an annular first fastening surface 61 facing the second axial direction X2. The intermediate plate 20 has an annular second fastening surface 62 facing the first axial direction X1 and an annular third fastening surface 63 facing the second axial direction X2. The housing has an annular fourth fastening surface 64 facing the first axial direction X1. The second main body portion 32 of the gearbox 30 has a fifth fastening surface 65 facing toward the motor housing. The motor housing 40 has a sixth fastening surface 66 facing toward the second main body portion.

[0048] With regard to the above-mentioned fastening surfaces, the first fastening surface 61 and the second fastening surface 62 contact each other. The third fastening surface 63 and the fourth fastening surface 64 contact each other. The fifth fastening surface 65 and the sixth fastening surface 66 contact each other. Of the two fastening surfaces that contact each other, one fastening surface has a protrusion 70 that protrudes toward the other fastening surface.

[0049] Between the first fastening surface 61 and the second fastening surface 62, two first convex portions 71 are provided on the side of the first fastening surface 61. Between the third fastening surface 63 and the fourth fastening surface 64, two second convex portions 72 are provided on the side of the third fastening surface 63. Between the fifth fastening surface 65 and the sixth fastening surface 66, a third convex portion 73 is provided on the side of the fifth fastening surface 65.

[0050] As shown in FIG. 5, the first protrusion 71 (protrusion 70) is formed long in the circumferential direction. The two first protrusions 71 are arranged point-symmetrically about the central axis O1. As shown in FIG. 6, the protrusion amount H1 of the first protrusion 71 is constant in the circumferential direction. The side surfaces 71a and 71b of the first protrusion 71 are angled 90° with respect to the first fastening surface 61. The protrusion amount H1 is preferably, for example, 50 μm to 200 μm, but the present disclosure is not limited to this value. The tip surface 71e of the first protrusion 71 is formed flat.

[0051] As shown in Fig. 5, a virtual line drawn from the central axis O1 to the third flange is referred to as a first virtual line K1. A virtual line passing through the central axis O1 and intersecting the first virtual line K1 at a 90° angle is referred to as a second virtual line K2. This second virtual line K2 passes through the circumferential center of the first protrusion 71. In other words, the two first protrusions 71 are disposed 90° apart from the two third flanges in the circumferential direction. In other words, the first protrusions 71 are disposed in locations on the first fastening surface 61 where the axial force of the first bolt 51 is unlikely to act.

[0052] Although not specifically shown, an imaginary line drawn from the two second protrusions 72 to the central axis O1 intersects with an imaginary line drawn from the second flange 23 to the central axis O1 at an angle of 90°. Therefore, the second protrusions 72 are also disposed at locations on the third fastening surface 63 where the axial force of the first bolt 51 is unlikely to act.

[0053] Similarly, an imaginary line drawn from the two third protrusions 73 to the central axis O3 intersects with an imaginary line drawn from the fifth flange to the central axis O3 at an angle of 90°. Therefore, the third protrusions 73 are also disposed at locations on the fifth fastening surface 65 where the axial force of the second bolts 52 is unlikely to act.

[0054] FIG. 7 is a cross-sectional view of the housing of the first embodiment cut along the same line as the cross-sectional view of FIG. 6 . According to the housing 1 of the first embodiment described above, the first convex portion 71 reliably abuts the opposing second fastening surface 62. Furthermore, the second convex portion 72 reliably contacts the opposing fourth fastening surface 64. Although not specifically shown, the third convex portion 73 contacts the opposing sixth fastening surface 66. Therefore, even at a location on the fastening surface where axial force is unlikely to act (a location 90° circumferentially offset from the flange), the opposing fastening surfaces contact each other, and no gap is formed. Therefore, the natural frequency of the partial housing does not change, and the natural frequency of the partial housing does not coincide with the vibration of the order components relative to rotor rotation. Therefore, noise is not generated from the housing 1 (partial housing).

[0055] In this embodiment, the two first bolts 51 are arranged in the vertical direction Z as viewed from the central axis O1. Furthermore, as shown in FIG. 4 , the slit 11a of the main body 11 is arranged downward as viewed from the central axis O1, and the main body 11 is fastened in the horizontal direction Y by the bracket 3 (see arrow B in FIG. 4 ). With this layout, gaps are likely to occur between the fastening surfaces (between the first fastening surface 61 and the second fastening surface 62, or between the third fastening surface 63 and the fourth fastening surface 64) located in the horizontal direction as viewed from the central axis O1. On the other hand, in this embodiment, the first convex portion 71 and the second convex portion 72 are arranged in the horizontal direction as viewed from the central axis O1, ensuring reliable contact between the opposing fastening surfaces. Therefore, the natural frequency of the partial housing does not change, and the natural frequency of the partial housing does not coincide with the vibration of the order components relative to the rotor rotation. Therefore, noise is not generated from the housing 1 (partial housing).

[0056] Although the first embodiment has been described above, the present invention is not limited to the above example. In the first embodiment, the first convex portion 71 is formed on the first fastening surface, but in the present disclosure, the first convex portion may be formed on the second fastening surface. Similarly, the second convex portion may be formed on the fourth fastening surface. Furthermore, the third convex portion may be formed on the fifth fastening surface.

[0057] In the first embodiment, two protrusions are formed on one fastening surface, but one protrusion may be formed on one fastening surface. In other words, the present disclosure is applicable as long as one or more protrusions are formed on one fastening surface.

[0058] In embodiment 1, convex portions 70 are formed between the first fastening surface 61 and the second fastening surface 62, between the third fastening surface 63 and the fourth fastening surface 64, and between the fifth fastening surface 65 and the sixth fastening surface 66, but convex portions 70 may be formed only between any one pair of fastening surfaces.

[0059] Although the housing of the embodiment includes the intermediate plate 20, the present disclosure does not necessarily include the intermediate plate 20. In other words, the housing may be configured such that the fastening surfaces of the gear box 30 and the housing 10 come into contact with each other.

[0060] Furthermore, although the fastening surfaces (first fastening surface 61, second fastening surface 62, third fastening surface 63, fourth fastening surface 64, fifth fastening surface 65, and sixth fastening surface 66) in the embodiment have a circular shape when viewed in the axial direction, the fastening surfaces of the present disclosure may have any shape when viewed in the axial direction as long as they are continuous in the circumferential direction. In other words, the fastening surfaces may have an oval or rectangular shape when viewed in the axial direction.

[0061] In addition, in the embodiment, the tip surfaces of the convex portions (such as the tip surface 71e of the first convex portion 71) are formed flat, but the present disclosure is not limited to this. In the present disclosure, the tip surfaces of the convex portions may have multiple small protrusions formed thereon or may be knurled. In addition, the present disclosure is not limited to fastening surfaces that are all flat, but may instead have multiple small protrusions formed thereon or be knurled.

[0062] Furthermore, the housing 1 of the present disclosure does not have to house all of the steering shaft 82, the input shaft 82a, the torsion bar, the output shaft 89, the torque sensor 90, the motor 91, the reduction gear 92, and the control device 93. The housing 1 of the present disclosure may house only one of the steering shaft 82, the input shaft 82a, the torsion bar, the output shaft 89, the torque sensor 90, the motor 91, the reduction gear 92, and the control device 93. Alternatively, the housing 1 of the present disclosure may house other components, and there are no particular limitations on the types of components to be housed.

[0063] In addition, in the embodiment, there are two each of the bolts (first bolts 51), the first flanges 13, and the second flanges 23, but in the present disclosure, there may be two or more. Note that when there are two or more each of the first flanges 13 and the second flanges 23, the first flanges 13 and the second flanges 25 are arranged rotationally symmetrically about the central axis O1. In other words, when there are three first flanges 13, they are arranged at 120° intervals.

[0064] Furthermore, although the convex portion in the embodiment is disposed circumferentially offset by 90° from the flange, the present disclosure is not limited to this. The convex portion may be disposed in any location where the axial force of the first bolt 51 is unlikely to act. In other words, the convex portion in the present disclosure may be disposed circumferentially offset from the flange around the central axis O1.

[0065] In this embodiment, thread grooves that thread onto the shanks of the bolts are formed on the inner circumferential surfaces of holes 35 a and 38 a, but in the present disclosure, thread grooves do not have to be formed on the inner circumferential surfaces of holes 35 a and 38 a. In other words, the shanks of the bolts may pass through holes 35 a and 38 a and thread onto the nuts.

[0066] Furthermore, the shape of the convex portion is not limited to the example shown in the embodiment, and modifications will be described below.

[0067] (Modification 1) FIG. 8 is a cross-sectional view of a convex portion of Modification 1 taken in the circumferential direction. As shown in FIG. 8, the side surfaces 71a and 71b of the convex portion 70A of Modification 1 are inclined with respect to the orthogonal direction (see imaginary line K10 in FIG. 8 ) perpendicular to the fastening surface 60. Therefore, the circumferential length H2 of the convex portion 70A gradually decreases from the base 71c toward the tip 71d. Even with this shape, the same effects as those of Embodiment 1 can be achieved. Note that in Modification 1, both the side surfaces 71a and 71b are inclined with respect to the orthogonal direction (see imaginary line K10 in FIG. 8 ). However, in the present disclosure, only one of the side surfaces 71a and 71b may be inclined with respect to the orthogonal direction (see imaginary line K10 in FIG. 8 ). Furthermore, in the present disclosure, the inclination angle of the side surface 71a with respect to the orthogonal direction (see imaginary line K10 in FIG. 8 ) and the inclination angle of the side surface 71b with respect to the orthogonal direction (see imaginary line K10 in FIG. 8 ) may be the same or different.

[0068] (Modification 2) Fig. 9 is a cross-sectional view of the protrusion 70B of Modification 2 cut in the circumferential direction. As shown in Fig. 9, the protrusion 70B is formed by pressing a part of the fastening surface 60 with a tool and lifting a part of the solid portion (see arrow A in Fig. 9). Note that the cross-sectional shape cut in the circumferential direction is a triangle with a pointed end toward the opposing fastening surface, but the present disclosure is not limited to this. Furthermore, in Modification 3, three (multiple) protrusions 70B are arranged as a set.

[0069] (Variation 3) FIG. 10 is a view of the protrusion of Variation 3 as viewed from the axial direction. As shown in FIG. 10 , the protrusion 70C is composed of a pair of partial protrusions 170, 170 spaced apart from each other in the circumferential direction. When viewed from the axial direction, a third virtual line K3 is a virtual line that intersects with a first virtual line K1 drawn from the central axis O1 to the third flange 35 at a 90° angle. When viewed from the axial direction, the third virtual line K3 passes between the pair of partial protrusions 170, 170. In other words, the pair of partial protrusions 170, 170 sandwich the third virtual line K3. According to Variation 3, a portion 161 of the first fastening surface 61 is disposed between the partial protrusions 170, 170 (on the third virtual line K3). Even in Variation 3, the fastening surfaces reliably contact each other, as in Embodiment 1, and noise is not generated from the housing.

[0070] Modified examples of the protrusion have been described above, but in the present disclosure, a plate material that is a separate component from the individual housing on which the fastening surfaces are formed may also be disposed between the two contacting fastening surfaces.

[0071] In addition, in the first embodiment, the two first bolts 51 are parallel to each other, but in the present disclosure, the two bolts do not have to be parallel to each other. In other words, one bolt may be inclined with respect to the other bolt.

[0072] REFERENCE SIGNS LIST 100 Electric power steering device 82 Steering shaft 89 Output shaft 90 Torque sensor 91 Motor 92 Reduction gear 93 Control device 94 MCU 1 Case 10 Housing 11 Main body 12 Cover 13 First flange 20 Intermediate plate 21 Partition wall 23 Second flange 30 Gear box 31 First main body 32 Second main body 35 Third flange 36 Cylindrical portion 37 Disk portion 38 Fourth flange 40 Motor housing 41 Fifth flange 61 First fastening surface 62 Second fastening surface 63 Third fastening surface 64 Fourth fastening surface 65 Fifth fastening surface 66 Sixth fastening surface 70, 70A, 70B Convex portion 71 First convex portion 72 Second convex portion 73 Third convex portion

Claims

1. A housing comprising: at least two or more partial housings; and two or more bolts fastening the partial housings together; each partial housing has a fastening surface that comes into contact with another partial housing when the bolt is fastened; the two or more partial housings include a first partial housing and a second partial housing; the first partial housing has: a first fastening surface that is the fastening surface; and two or more first flanges that are arranged on the outer periphery of the first fastening surface and have holes through which the shanks of the bolts are inserted; the second partial housing has: a second fastening surface that is the fastening surface and faces the first fastening surface; and two or more second flanges that are arranged on the outer periphery of the second fastening surface and have holes through which the shanks of the bolts are inserted and face the first flange; one of the first fastening surface and the second fastening surface is provided with at least one protrusion that protrudes toward the other fastening surface of the first fastening surface and the second fastening surface; the protrusion is disposed at a position offset in a circumferential direction from the first flange about a center of the first fastening surface.

2. The electric power steering device according to claim 1, wherein the housing houses a steering shaft, an input shaft, a torsion bar, an output shaft, a torque sensor, a motor, and a reduction gear.

3. The electric power steering device according to claim 1, wherein the number of the bolts is two, the number of the first flanges is two, the two first flanges are arranged point-symmetrically around the center of the first fastening surface, and the number of the second flanges is two.

4. An electric power steering device as described in claim 1, wherein, when viewed from a direction perpendicular to the first fastening surface, the angle formed by a first imaginary line drawn from the center of the first fastening surface to the first flange and a second imaginary line drawn from the center of the first fastening surface to the convex portion is 90°.

5. An electric power steering device as described in claim 1, wherein the convex portion is a pair of partial convex portions arranged at a distance from each other in the circumferential direction, and when viewed from a direction perpendicular to the first fastening surface, an angle formed by a first imaginary line drawn from the center of the first fastening surface to the first flange and a third imaginary line drawn from the center of the first fastening surface between the pair of partial convex portions is 90°.

6. The electric power steering device according to claim 1, wherein two of the protrusions are provided, and the two protrusions are arranged point-symmetrically with respect to the center of the first fastening surface.

7. An electric power steering device according to claim 1, wherein the length of the convex portion extending in the circumferential direction along the fastening surface gradually decreases from the base of the convex portion toward the tip of the convex portion.

8. An electric power steering device according to claim 2, wherein the first partial housing is a gear box that houses at least the reduction gear device, and the second partial housing is a housing.

9. An electric power steering device according to claim 2, wherein the first partial housing is a gear box that houses at least the reduction gear device, and the second partial housing is a motor housing that supports the motor.

10. An electric power steering device as described in claim 2, wherein the two or more partial housings include a third partial housing arranged in the opposite direction to the first partial housing when viewed from the second partial housing, the second partial housing having a third fastening surface arranged on the back side of the second fastening surface, the third partial housing having: a fourth fastening surface that is the fastening surface and faces the third fastening surface; and two third flanges that are arranged on the outer periphery of the fourth fastening surface, have through holes through which the shanks of the bolts are inserted, and face the second flanges, one of the third fastening surface and the fourth fastening surface is provided with at least one or more convex portions that protrude toward the other of the third fastening surface and the fourth fastening surface, and the convex portion provided on the first fastening surface or the second fastening surface overlaps with the convex portion provided on the third fastening surface or the fourth fastening surface when viewed from a direction perpendicular to the first fastening surface.

11. An electric power steering device according to claim 10, wherein the first partial housing is a gear box that accommodates at least the reduction gear device, the second partial housing is an annular intermediate plate, and the third partial housing is a housing.

12. An electric power steering device according to any one of claims 1 to 11, wherein the protrusion is formed as a separate part from the partial housing.

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