Electric power steering device

Abstract

To provide a more compact electric power steering device. [Solution] The electric power steering device includes an assist pinion shaft, a worm wheel attached to the Z2-side end of the assist pinion shaft, a worm shaft having shaft teeth that mesh with the wheel teeth, and a housing that houses the worm shaft and the worm wheel. The portion of the wheel teeth that meshes with the shaft teeth is a first portion, and the portion located on the opposite side of the central axis from the first portion is a second portion. A first distance from the Z1-side end face of the first portion to the tip of the housing end is greater than a second distance from the Z1-side end face of the second portion to the tip of the housing end.

Description

[Technical Field]

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

[0002] The electric power steering device of Patent Document 1 includes a pinion shaft, a worm wheel, a worm shaft, a housing, and a lid member (cover member). Specifically, a worm wheel is attached to the axial end of the pinion shaft, and the worm wheel meshes with the worm shaft. The housing is provided with an accommodation space that accommodates the pinion shaft, the worm wheel, and the worm shaft. The end of the housing is open, and the opening is covered with a lid member (cover member). Specifically, an attachment portion is provided at the end of the housing, and the lid member is attached to the attachment portion, thereby covering the opening with the lid member (cover member).

[0003] The lid member (cover member) faces the worm wheel and is disposed approximately parallel to the worm wheel. The reason for this will be briefly explained below. The accommodation space and attachment portion of the housing may be formed, for example, by processing (e.g., cutting) using a machine tool. In this case, if the lid member is disposed approximately parallel to the worm wheel, the orientation of the machine tool relative to the housing will be the same when processing the accommodation space and when processing the attachment portion, making the machining work easier. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-199926 Summary of the Invention [Problem to be solved by the invention]

[0005] A more compact electric power steering device is desired.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a more compact electric power steering device. [Means for solving the problem]

[0007] In order to achieve the above object, an electric power steering device according to one embodiment includes: a rack shaft extending in a first direction and having rack teeth on an outer periphery; an assist pinion shaft extending in a second direction intersecting the first direction and having pinion teeth that mesh with the rack teeth on an outer periphery on one side of the second direction; a worm wheel attached to an end of the assist pinion shaft on the other side in the second direction and having wheel teeth on its outer periphery; a worm shaft having shaft teeth that mesh with the wheel teeth and that rotates by the driving force of an electric motor; and a housing that accommodates the worm shaft and the worm wheel and has an opening on the inner periphery of an end of the housing. a first portion of the wheel tooth portion that is in mesh with the shaft tooth portion, and a second portion of the wheel tooth portion that is located on the opposite side of the first portion across the central axis of the assist pinion shaft, wherein in a cross section that includes the central axis of the assist pinion shaft, the first portion, and the second portion, a first distance from an end face of the first portion on the other side in the second direction to a tip of the housing end portion that is located on the first portion side with respect to the central axis of the assist pinion shaft is greater than a second distance from an end face of the second portion on the other side in the second direction to a tip of the housing end portion that is located on the second portion side with respect to the central axis of the assist pinion shaft.

[0008] As described above, in the electric power steering device of the present disclosure, the first distance is greater than the second distance. In other words, the second distance is less than the first distance. In contrast, in Patent Document 1, the second distance and the first distance are the same. To reduce the size of the electric power steering device, it is desirable to position the tip of the housing end further downward (on one side in the second direction). However, in Patent Document 1, the lid member (cover member) is positioned approximately parallel to the worm wheel and as close as possible to the worm wheel. This makes it difficult to further reduce the height of the housing in Patent Document 1. Here, if the direction intersecting the first and second directions is defined as a third direction, in the present disclosure, the height of the tip of the housing end on the second part side is lower than the tip of the housing end on the first part side, and the opening is positioned so as to be oblique when viewed from the third direction. This allows the height of the housing to be lower than that of Patent Document 1. As described above, the present disclosure can provide a more compact electric power steering device.

[0009] In a desirable aspect, a lid member that covers the opening is provided at the housing end of the housing, and the housing end of the housing includes an annular portion extending in an axial direction around the central axis of the assist pinion shaft and a flange protruding radially outward from the annular portion, and the lid member can be attached to the flange, and the flange is arranged at a portion of the annular portion excluding a third portion, a fourth portion, a fifth portion, and a sixth portion, and when viewed from the second direction, the third portion and the fourth portion are intersections of the annular portion and a first straight line that passes through the central axis of the assist pinion shaft and extends in the first direction, and the fifth portion overlaps with the first portion, and the sixth portion overlaps with the second portion.

[0010] Thus, in the present disclosure, the flanges provided on the annular portion of the housing are arranged at positions on the annular portion excluding the third position, the fourth position, the fifth position, and the sixth position.

[0011] Here, it is assumed that a fastening member is used to attach the lid member to the flange. That is, the fastening member is attached to the flange by passing the fastening member through the through-hole of the lid member from the upper side (the other side in the second direction) of the lid member and then fastening it to the flange.

[0012] First, when viewed from the second direction, the fifth portion overlaps the first portion, and the sixth portion overlaps the second portion. If a flange is provided at the sixth portion, the fastening member protrudes upward from the portion of the top surface of the cover member that corresponds to the sixth portion, and the height of the housing on the sixth portion side and the second portion side increases by the amount of the protruding portion of the fastening member. Therefore, the fifth and sixth portions are not desirable locations for locating a flange.

[0013] Furthermore, various components, such as mounting components for an electric motor, are disposed near the third and fourth positions. Therefore, if a flange is provided in the third or fourth position, the flange may interfere with the mounting components, etc., and therefore the third and fourth positions are not desirable locations for disposing the flange. For these reasons, it is desirable to dispose the flange in a location other than the third, fourth, fifth, and sixth positions.

[0014] In a preferred embodiment, the lid member comprises a lid main body portion that covers the opening, and a ring-shaped protrusion portion that protrudes from the peripheral edge portion of the lid main body portion to one side in the second direction, the protrusion portion being arranged on the inner peripheral side of the housing end portion of the housing, and a ring-shaped O-ring extending circumferentially is provided between the outer periphery of the protrusion portion and the housing end portion of the housing.

[0015] In this manner, with the protrusion inserted into the inner periphery of the housing end, an O-ring is provided between the protrusion and the inner periphery of the housing. That is, the inner periphery of the housing and the protrusion are sealed by an O-ring axial seal. Here, it is also possible to apply a surface seal in which an O-ring is provided between the top surface of the housing end and the lid member. However, if a force is applied to the lid member, for example, in an upward direction (the other side in the second direction), the lid member moves slightly upward from the upper end of the housing, thereby reducing the sealing effect of the surface seal. For these reasons, it is desirable to seal the gap between the inner periphery of the housing and the protrusion with an O-ring axial seal, as in the present disclosure.

[0016] In a preferred embodiment, when viewed from the first direction, an end of the protrusion on one side in the second direction intersects with an end face of the assist pinion shaft on the other side in the second direction.

[0017] When reducing the size of the electric power steering device, it is desirable to position the cover member lower (on one side in the second direction). Therefore, when viewed from the first direction, the electric power steering device can be made smaller when the lower end of the protrusion (the end on one side in the second direction) intersects with the upper end face of the assist pinion shaft, as in the present disclosure, than when the lower end of the protrusion (the end on one side in the second direction) does not intersect with the upper end face of the assist pinion shaft (the end face on the other side in the second direction).

[0018] In a preferred embodiment, the worm shaft is located on the opposite side of the rack shaft with the assist pinion shaft in between. If the worm shaft were located on the rack shaft side of the assist pinion shaft, many parts would be concentrated on the rack shaft side, which could result in an increased size of the electric power steering device. Therefore, by locating the rack shaft on one side of the assist pinion shaft and the worm shaft on the other side, the electric power steering device can be made even more compact. [Effects of the Invention]

[0019] According to the present disclosure, a more compact electric power steering device is provided. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of an electric power steering device according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing a part of FIG. [Figure 3] FIG. 3 is a schematic diagram of FIG. 2 as viewed from the X1 side. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is an enlarged cross-sectional view of a part of FIG. [Figure 6] FIG. 6 is a schematic diagram of a part of FIG. 2 viewed from the Z1 side. [Figure 7] FIG. 7 is a schematic diagram showing a part of FIG. 6 with the cover member removed. DETAILED DESCRIPTION OF THE INVENTION

[0021] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the components described below can be combined as appropriate. Furthermore, parts with the same structure are given the same reference numerals and descriptions thereof will be omitted. In this embodiment, the X direction is the first direction, the Z direction is the second direction, and the Y direction is the third direction. The Z direction intersects with the X direction. The Y direction intersects with the X and Z directions. Specifically, the Y direction (third direction) is a direction parallel to the upper surface 424c of the lid member 424 (see FIG. 5), which will be described later.

[0022] The angle between the X direction and the Z direction can be determined arbitrarily. For example, the angle between the X direction and the Z direction may be a right angle, an acute angle, or an obtuse angle.

[0023] An electric power steering device according to an embodiment will be described. Fig. 1 is a schematic diagram of the electric power steering device according to the embodiment. Fig. 2 is a perspective view showing a part of Fig. 1. Fig. 3 is a schematic diagram of Fig. 2 as viewed from the X1 side. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 2. Fig. 5 is an enlarged cross-sectional view of a part of Fig. 4.

[0024] 1, the electric power steering device 80 includes a steering wheel 81, a first steering shaft 82, a second steering shaft 83, a steering pinion shaft 84, a rack shaft 85, a tie rod 86, an assist pinion shaft 1, a worm wheel 2, a worm shaft 3, an electric motor 100, a first housing 41, and a second housing 42. The electric power steering device 80 is, for example, a so-called dual pinion type steering device.

[0025] As shown in Fig. 1, a steering wheel 81 is connected to a first steering shaft 82, which is connected to a second steering shaft 83 via a universal joint 821. The second steering shaft 83 is connected to a steering pinion shaft 84 via a universal joint 831. Pinion teeth 841 are formed on the outer periphery of the lower end of the steering pinion shaft 84.

[0026] As shown in FIG. 1 , the rack shaft 85 extends in the X direction (first direction). Here, if the central axis of the rack shaft 85 is defined as a central axis AX2, the axial direction of the central axis AX2 is along the X direction (first direction). That is, the rack shaft 85 extends in the axial direction of the central axis AX2 and is rotatable around the central axis AX2. The X direction (first direction) is, for example, the width direction of the vehicle. Rack teeth 851 are provided on the outer periphery of the X2 side of the rack shaft 85. The rack teeth 851 mesh with pinion teeth 841 of the steering pinion shaft 84. Rack teeth 852 are provided on the outer periphery of the X1 side of the rack shaft 85. The rack teeth 852 mesh with pinion teeth 1 a of the assist pinion shaft 1. Both ends of the rack shaft 85 on the X1 side and the X2 side are connected to wheels 101 via tie rods 86.

[0027] As described above, the steering wheel 81 is connected to the steering pinion shaft 84 via the first steering shaft 82 and the second steering shaft 83. Therefore, when the driver applies steering torque to the steering wheel 81 in the left or right direction, the steering torque is transmitted to the steering pinion shaft 84 via the first steering shaft 82 and the second steering shaft 83. Then, because the pinion teeth 841 of the steering pinion shaft 84 mesh with the rack teeth 851, the steering torque is converted into a force that moves the rack shaft 85 in the X direction.

[0028] In addition, a steering torque sensor (not shown) detects the steering torque applied to the steering wheel 81, and a controller (not shown) supplies current to the electric motor 100 in accordance with the detected steering torque. When current is supplied to the electric motor 100, the assist torque generated by the electric motor 100 is transmitted to the assist pinion shaft 1 connected to the electric motor 100 via the worm wheel 2 and the worm shaft 3, and an assist force is generated that moves the rack shaft 85 connected to the assist pinion shaft 1 in the X direction.

[0029] That is, by driving the electric motor 100 in accordance with the steering torque generated by steering the steering wheel 81, it is possible to assist the rack shaft 85 in moving in the X direction.

[0030] As shown in FIGS. 1 and 2, the rack shaft 85, the steering pinion shaft 84, the assist pinion shaft 1, the worm wheel 2, the worm shaft 3, and the electric motor 100 are housed in a first housing 41 and a second housing 42. The first housing 41 is located on the X2 side, and the second housing 42 is located on the X1 side. A flange 411 is provided at the X1-side end of the first housing 41, and a flange 421 is provided at the X2-side end of the second housing 42. The first housing 41 and the second housing 42 are connected by fixing the flanges 411 and 421 together. As shown in FIG. 2, a vehicle body mounting member 103 is attached to the X2-side end of the first housing 41 and the X1-side end of the second housing 42, respectively. A through hole 103a is provided in the vehicle body mounting member 103, and a fastening member (e.g., a bolt) is inserted into the through hole 103a. That is, the first housing 41 and the second housing 42 are attached to the vehicle body by passing a fastening member through the through-hole 103a and then fastening it to the vehicle body. As shown in Fig. 1, a speed reducer accommodating portion 423, which is part of the second housing 42, accommodates a speed reducer mechanism 200 including the worm wheel 2 and the worm shaft 3 inside.

[0031] 2 and 3, the rack shaft 85 is accommodated inside the rack shaft accommodating portion 422 of the second housing 42. As shown in FIG. 4, the assist pinion shaft 1 and the worm wheel 2 are accommodated inside the reducer accommodating portion 423 extending from the rack shaft accommodating portion 422 to the Z1 side. The worm shaft 3 and the electric motor 100 are disposed on the Y1 side of the assist pinion shaft 1 and the worm wheel 2. The assist pinion shaft 1, the worm wheel 2, and the worm shaft 3 will be described in detail below.

[0032] As shown in FIGS. 4 and 5, the assist pinion shaft 1 extends in the axial direction (second direction, Z direction) of the central axis AX1. The second direction (Z direction) is a direction intersecting the first direction (X direction). The assist pinion shaft 1 is rotatable around the central axis AX1. The assist pinion shaft 1 has pinion teeth 1a on the outer periphery on one side (Z2 side) in the axial direction (second direction, Z direction). One axial side (Z2 side) of the assist pinion shaft 1 is rotatably supported by the reducer accommodating section 423 (housing) via a bearing 110. The other axial side (Z1 side) of the assist pinion shaft 1 is rotatably supported by the reducer accommodating section 423 (housing) via a bearing 111.

[0033] As shown in Figures 4 and 5, a worm wheel 2 is attached to the other axial side (Z1 side) of the assist pinion shaft 1, closer to the Z1 side than the bearing 111. That is, the worm wheel 2 is attached to the end 1b of the assist pinion shaft 1 on the other side in the second direction. The worm wheel 2 has a core metal portion 21 and a wheel tooth portion 22. The core metal portion 21 is made of, for example, metal, and has an annular shape extending along the axial direction about the central axis AX1. The wheel tooth portion 22 is provided on the outer periphery of the core metal portion 21. The wheel tooth portion 22 is made of, for example, resin. The wheel tooth portion 22 has an annular shape extending along the axial direction about the central axis AX1.

[0034] As shown in FIGS. 4 and 5 , the worm shaft 3 is disposed on the Y1 side, which is one side in the Y direction (third direction), of the worm wheel 2. In other words, the worm shaft 3 is located on the opposite side of the rack shaft 85 across the assist pinion shaft 1. The worm shaft 3 has shaft teeth 31 that mesh with the wheel teeth 22. The worm shaft 3 extends in the axial direction of the central axis AX3 and is rotatable around the central axis AX3. The worm shaft 3 is rotated by the driving force of the electric motor 100.

[0035] 4 and 5, the reducer accommodating portion 423 (housing) accommodates the worm shaft 3, the worm wheel 2, and the assist pinion shaft 1. An opening 104 is provided on the inner peripheral side of a housing end portion 427 on the other side (Z1 side) in the second direction (Z direction) of the reducer accommodating portion 423 (housing).

[0036] 5, a housing end 427 on the Z1 side of the reducer housing portion 423 (housing) has an annular portion 420. The annular portion 420 has an annular shape along the direction around the central axis AX1 (see FIG. 7). The opening 104 is covered with a cover member 424.

[0037] As shown in FIG. 5, a portion of the wheel tooth portion 22 that meshes with the shaft tooth portion 31 is the first portion P1. A portion of the wheel tooth portion 22 that is located on the opposite side of the center axis AX1 from the first portion P1 is the second portion P2. In addition, in the reducer accommodating portion 423 (housing), a portion that is located on the Y1 side (first portion P1 side) of the center axis AX1 is referred to as the motor-side housing portion 44. In the reducer accommodating portion 423 (housing), a portion that is located on the Y2 side (second portion P2 side) of the center axis AX1 is referred to as the anti-motor-side housing portion 43. In addition, an end face 22a is provided at the Z1-side end of the first portion P1. The end face 22a extends perpendicular to the center axis AX1. In addition, an end face 22b is provided at the Z1-side end of the second portion P2. The end face 22b extends perpendicular to the center axis AX1.

[0038] 5, the distance along the Z direction between the end face 22a and the tip 44a on the Z1 side of the housing end 427 of the motor-side housing part 44 is a first distance D1. The distance along the Z direction between the end face 22b and the tip 43a on the Z1 side of the housing end 427 of the anti-motor-side housing part 43 is a second distance D2. The first distance D1 is greater than the second distance D2. In other words, the second distance D2 is smaller than the first distance D1.

[0039] As shown in FIG. 5, the lid member 424 includes a lid main body 425 and a protruding portion 426. The lid main body 425 has a disk shape that covers the opening 104. The protruding portion 426 has an annular shape that protrudes from the peripheral edge of the lid main body 425 toward the Z2 side. The protruding portion 426 is disposed on the inner circumferential side of the annular portion 420. A circumferentially extending annular O-ring 102 is provided between the outer periphery of the protruding portion 426 and the annular portion 420. Specifically, a groove recessed radially inward (toward the inner periphery) is provided on the outer periphery of the protruding portion 426, and the O-ring 102 is accommodated in the groove. As shown in FIG. 5, when viewed from the X direction, a tip 426a on the Z2 side of the protruding portion 426 forms a straight line extending in the Y direction. An end face 1c on the Z1 side of the assist pinion shaft 1 extends perpendicular to the central axis AX1. Furthermore, a tip 426a of the protrusion 426 on the Z2 side intersects with the end face 1c.

[0040] Fig. 6 is a schematic diagram of a portion of Fig. 2 as viewed from the Z1 side. Fig. 7 is a schematic diagram showing a portion of Fig. 6 with the cover member removed. Note that in Fig. 6, the axial direction of the central axis AX1 is slightly offset from the Z direction (second direction). That is, the central axis AX1 is not completely perpendicular to the plane of Fig. 6, and in Fig. 6, the intersection of the central axis AX1 and the upper surface of the cover member 424 is depicted as point AX1.

[0041] As shown in FIG. 7, a housing end 427 on the Z1 side of the reducer accommodating portion 423 (housing) includes an annular portion 420 and flanges 420a and 420b. The annular portion 420 extends annularly around the central axis AX1. The flanges 420a and 420b protrude radially outward from the annular portion 420. A cover member 424 can be attached to the flanges 420a and 420b. A bolt hole 420c is formed in the flange 420a, and a bolt hole 420d is formed in the flange 420b. The flanges 420a and 420b are disposed in portions of the annular portion 420 excluding the third portion P3, the fourth portion P4, the fifth portion P5, and the sixth portion P6. The positions of the third portion P3 to the sixth portion P6 will be described with reference to FIG. 6.

[0042] In Fig. 6, a cover member 424 is attached to the upper side of the annular portion 420 and flanges 420a, 420b in Fig. 7. The cover member 424 is provided with flanges 424a, 424b. The flange 424a is fastened onto the flange 420a with bolts BL. The flange 424b is fastened onto the flange 420b with bolts BL.

[0043] As shown in FIG. 6, a first line L1 is a line that passes through the central axis AX1 and extends in the X direction (first direction). A second line L2 is a line that passes through the central axis AX1 and extends in the Y direction (third direction). The third portion P3 and the fourth portion P4 are intersections of the first line L1 and the annular portion 420 when viewed from the Z direction. The third portion P3 is on the X2 side of the central axis AX1, and the fourth portion P4 is on the X1 side of the central axis AX1. The third line L3 is a line that connects the center of the bolt BL that fastens the flange 424a and the flange 420a and the center of the bolt BL that fastens the flange 424b and the flange 420b. The fifth portion P5 and the sixth portion P6 are intersections of the second line L2 and the annular portion 420 when viewed from the Z direction. The fifth portion P5 is on the Y1 side of the central axis AX1, and the sixth portion P6 is on the Y2 side of the central axis AX1. When viewed from the Z direction (second direction), the fifth portion P5 overlaps with the first portion P1, and the sixth portion P6 overlaps with the second portion P2.

[0044] Therefore, the flanges 420a, 420b are arranged in the range from the third region P3 to the sixth region P6, the range from the sixth region P6 to the fourth region P4, the range from the fourth region P4 to the fifth region P5, and the range from the fifth region P5 to the third region P3 along the circumferential direction of the annular portion 420. In other words, when viewed from the surface of the cover member 424, the first straight line L1 and the third straight line L3 intersect at a predetermined angle.

[0045] 6, the motor accommodating housing 428 is fixed to the motor mounting plate 45. The electric motor 100 is attached to the motor mounting plate 45 and housed inside the motor accommodating housing 428. The motor mounting plate 45 extends in the Y direction. If the flange 420a were located at the third position P3, the flange 420a would be close to the motor mounting plate 45, and therefore the distance between the annular portion 420 and the motor mounting plate 45 would need to be increased.

[0046] As described above, the electric power steering device 80 according to this embodiment includes the rack shaft 85 that extends in the X direction (first direction) and has rack teeth 852 on its outer periphery, the assist pinion shaft 1 that has pinion teeth 1a on its outer periphery on the Z2 side (one side) in the Z direction (second direction), the worm wheel 2 that is attached to the Z1 side end of the assist pinion shaft 1 and has wheel tooth portions 22 on its outer periphery, the worm shaft 3 that has shaft tooth portions 31 that mesh with the wheel tooth portions 22 and rotates by the driving force of the electric motor 100, and the reducer accommodating portion 423 (housing) that accommodates the worm shaft 3 and the worm wheel 2 and has an opening 104 on the inner periphery of the Z1 side end. A portion of the wheel tooth portion 22 that meshes with the shaft tooth portion 31 is a first portion P1, and a portion of the wheel tooth portion 22 that is located on the opposite side of the first portion P1 across the central axis AX1 of the assist pinion shaft 1 is a second portion P2. In a cross section including the central axis AX1 of the assist pinion shaft 1, the first portion P1, and the second portion P2, a first distance D1 from an end face 22a on the Z1 side of the first portion P1 to a tip end 44a of a housing end 427 that is located on the first portion P1 side with respect to the central axis AX1 is greater than a second distance D2 from an end face 22b on the Z1 side of the second portion P2 to a tip end 43a of the housing end 427 that is located on the second portion P2 side with respect to the central axis AX1.

[0047] As described above, in the electric power steering device 80 of this embodiment, the first distance D1 is greater than the second distance D2. In other words, the second distance D2 is smaller than the first distance D1. In contrast, in Patent Document 1, the second distance and the first distance are the same. Here, in order to reduce the size of the electric power steering device 80, it is desirable to position the tips 43a and 44a of the housing end 427 further downward (toward the Z2 side). However, in Patent Document 1, the lid member (cover member) is positioned approximately parallel to the worm wheel. Therefore, in Patent Document 1, the lid member cannot be positioned closer to the worm wheel, making it difficult to lower the height of the housing. In this regard, in this embodiment, the height of the wall surface of the opening 104 of the reducer accommodating portion 423 (housing) at a position far from the worm shaft 3 (the second distance D2 based on the wheel tooth portion 22) is set lower than the height of the wall surface of the opening 104 of the reducer accommodating portion 423 (housing) at a position close to the worm shaft 3 (the first distance D1 based on the wheel tooth portion 22). That is, according to this embodiment, at a position far from the worm shaft 3, the reducer accommodating portion 423 (housing) can be prevented from protruding upward (toward the Z1 side).

[0048] In other words, the height of the tip 43a is made lower than the tip 44a, and the opening 104 is disposed so as to be oblique when viewed from the Y direction, so that the height of the reducer accommodating portion 423 (housing) can be made lower than that of Patent Document 1. In this way, in this embodiment, it is possible to provide an electric power steering device 80 that is more compact.

[0049] A lid member 424 that covers the opening 104 is provided at a casing end 427 of the reducer accommodating portion 423 (casing). The casing end 427 includes an annular portion 420 that extends in the axial direction around the central axis AX1, and flanges 420a and 420b that protrude radially outward from the annular portion 420, and the lid member 424 can be attached to the flanges 420a and 420b. The flanges 420a and 420b are arranged at portions of the annular portion 420 excluding the third portion P3, the fourth portion P4, the fifth portion P5, and the sixth portion P6. When viewed from the Z direction (second direction), the third portion P3 and the fourth portion P4 are intersections between the annular portion 420 and a first straight line L1 that passes through the central axis AX1 and extends in the X direction (first direction), and the fifth portion P5 and the sixth portion P6 are intersections between the annular portion 420 and a second straight line L2 that passes through the central axis AX1 and extends in the Y direction (third direction), with the fifth portion P5 overlapping with the first portion P1 and the sixth portion P6 overlapping with the second portion P2.

[0050] Thus, in this embodiment, the flanges 420a, 420b provided on the annular portion 420 of the reducer accommodating portion 423 (housing) are arranged in the portions of the annular portion 420 excluding the third portion P3, the fourth portion P4, the fifth portion P5, and the sixth portion P6.

[0051] Here, it is assumed that bolts BL (fastening members), for example, are used to attach the cover member 424 to the flanges 420a, 420b. That is, the bolts BL are passed through through holes in the cover member 424 from, for example, the upper side (the other side in the second direction) of the cover member 424 and then fastened to the flanges 420a, 420b, thereby attaching the cover member 424 to the flanges 420a, 420b using the bolts BL.

[0052] First, when viewed from the top-bottom direction (Z direction, second direction), the fifth portion P5 overlaps with the first portion P1, and the sixth portion P6 overlaps with the second portion P2. If flanges 420a and 420b are provided at the sixth portion P6, the bolts BL protrude upward from the portions of the top surface of the cover member 424 corresponding to the sixth portion P6, and the height of the reducer accommodating portion 423 (housing) on ​​the sixth portion P6 side and the second portion P2 side increases by the amount of the protruding portions of the bolts BL. Therefore, the fifth portion P5 and the sixth portion P6 are not desirable locations for arranging the flanges 420a and 420b.

[0053] Furthermore, components including, for example, the motor mounting plate 45 of the electric motor 100 are disposed near the third portion P3 and the fourth portion P4. Therefore, if the flanges 420a, 420b are provided at the third portion P3 or the fourth portion P4, the flanges 420a, 420b may interfere with the motor mounting plate 45, and therefore the third portion P3 and the fourth portion P4 are not desirable locations for arranging the flanges 420a, 420b. For these reasons, it is desirable to arrange the flanges 420a, 420b at a location other than the third portion P3, the fourth portion P4, the fifth portion P5, and the sixth portion P6.

[0054] The lid member 424 includes a lid main body 425 that covers the opening 104, and an annular protrusion 426 that protrudes toward the Z2 side from the peripheral edge of the lid main body 425. The protrusion 426 is disposed on the inner circumferential side of a housing end 427. An annular O-ring 102 extending in the circumferential direction is provided between the outer periphery of the protrusion 426 and the housing end 427.

[0055] In this manner, with the protruding portion 426 inserted into the inner periphery of the housing end 427 of the reducer accommodating portion 423 (housing), the O-ring 102 is provided between the protruding portion 426 and the inner periphery of the housing end 427. That is, the inner periphery of the housing end 427 and the protruding portion 426 are sealed by an axial seal using the O-ring 102. Here, it is also possible to apply a surface seal in which the O-ring 102 is provided between the upper surface of the housing end 427 and the cover member 424. However, if a force is applied to the cover member 424, for example, in an upward direction (the other side in the second direction), the cover member 424 moves slightly upward from the housing end 427, thereby reducing the sealing effect of the surface seal. For the above reasons, it is desirable to seal the gap between the inner periphery of the reducer accommodating portion 423 (housing) and the protruding portion 426 with an axial seal using the O-ring 102, as in this embodiment.

[0056] When viewed from the X direction (first direction), a tip 426a of the protrusion 426 on the Z2 side intersects with an end face 1c of the assist pinion shaft 1 on the Z1 side.

[0057] In order to reduce the size of the electric power steering device 80, it is desirable to dispose the cover member 424 lower (on one side in the second direction). Therefore, when viewed from the X direction (first direction), the electric power steering device 80 can be reduced in size more effectively if the lower end (tip 426a) of the protrusion 426 intersects with the upper end face 1c of the assist pinion shaft 1, as in this embodiment, than if the lower end (tip 426a) of the protrusion 426 does not intersect with the upper end face 1c of the assist pinion shaft 1 (the end face on the other side in the second direction).

[0058] It is desirable that the worm shaft 3 be located on the opposite side of the rack shaft 85 with the assist pinion shaft 1 in between. If the worm shaft 3 were located on the rack shaft 85 side of the assist pinion shaft 1, many parts would be concentrated on the rack shaft 85 side, which could result in the electric power steering device 80 becoming larger. Therefore, by arranging the rack shaft 85 on one side of the assist pinion shaft 1 and the worm shaft 3 on the other side, the electric power steering device 80 can be made even more compact. [Explanation of symbols]

[0059] 1 Assist pinion shaft 1a Pinion teeth 1b end 1c end face 2 worm wheels 3 worm shaft 21 Core metal part 22 Wheel tooth 22a, 22b end face 31 Shaft teeth 41 First Housing 42 Second Housing 43 Opposite motor side housing 43a Tip 44 Motor side housing part 44a tip 45 Motor mounting plate 80 Electric power steering device 81 Steering wheel 82 First steering shaft 83 Second steering shaft 84 Steering pinion shaft 85 Rack shaft 86 tie rod 100 electric motor 101 Wheels 102 O-ring 103 Body mounting member 103a Through hole 104 Opening 200 Reduction mechanism 411 flange 420 Circular section 420a, 420b flanges 420c, 420d bolt holes 421 flange 422 Rack shaft housing 423 Reducer housing 424 Lid member 424a, 424b flanges 424c top surface 425 Lid body part 426 Protrusion 426a Tip 427 Housing edge 428 Motor housing 821 Universal Joint 831 Universal Joint 841 Pinion teeth 851 rack teeth 852 rack teeth AX1 center axis AX2 center axis AX3 center axis BL Bolt D1 First distance D2 2nd distance L1 1st straight line L2 2nd straight line L3 3rd straight line P1 1st part P2 2nd part P3 3rd part P4 4th part P5 5th part P6 6th part

Claims

1. a rack shaft extending in a first direction and having rack teeth on an outer periphery thereof; an assist pinion shaft extending in a second direction intersecting the first direction and having pinion teeth that mesh with the rack teeth on an outer periphery on one side of the second direction; a worm wheel attached to the other end of the assist pinion shaft in the second direction and having a wheel tooth portion on its outer periphery; a worm shaft having shaft teeth that mesh with the wheel teeth and that is rotated by the driving force of an electric motor; a housing that accommodates the worm shaft and the worm wheel and has an opening provided on an inner peripheral side of an end of the housing on the other side in the second direction, a portion of the wheel tooth portion that is in mesh with the shaft tooth portion is a first portion, and a portion of the wheel tooth portion that is located on the opposite side of the first portion across the central axis of the assist pinion shaft is a second portion, In a cross section including a central axis of the assist pinion shaft, the first portion, and the second portion, a first distance from an end surface of the first portion on the other side in the second direction to a tip of the housing end portion located on the first portion side with respect to the central axis of the assist pinion shaft, a second distance from an end face of the second portion on the other side in the second direction to a tip of the housing end portion located on the second portion side with respect to the central axis of the assist pinion shaft, a cover member for covering the opening is provided at the housing end of the housing, the lid member includes a lid main body portion that covers the opening, and an annular protruding portion that protrudes from a peripheral edge portion of the lid main body portion to one side in the second direction, the protruding portion being disposed on an inner peripheral side of the housing end portion, The inner circumferential surface of the housing end portion is a first inner circumferential surface disposed opposite an outer circumferential surface of the protrusion of the cover member; a second inner circumferential surface located on one side in the second direction relative to the first inner circumferential surface, an outer peripheral surface of the protrusion and the first inner peripheral surface extend in a direction inclined with respect to a central axis of the assist pinion shaft and perpendicular to the lid main body; The second inner peripheral surface extends along a direction around a central axis of the assist pinion shaft. Electric power steering device.

2. a rack shaft extending in a first direction and having rack teeth on an outer periphery thereof; an assist pinion shaft extending in a second direction intersecting the first direction and having pinion teeth that mesh with the rack teeth on an outer periphery on one side of the second direction; a worm wheel attached to the other end of the assist pinion shaft in the second direction and having a wheel tooth portion on its outer periphery; a worm shaft having shaft teeth that mesh with the wheel teeth and that is rotated by the driving force of an electric motor; a housing that accommodates the worm shaft and the worm wheel and has an opening provided on an inner peripheral side of an end of the housing on the other side in the second direction, a portion of the wheel tooth portion that is in mesh with the shaft tooth portion is a first portion, and a portion of the wheel tooth portion that is located on the opposite side of the first portion across the central axis of the assist pinion shaft is a second portion, In a cross section including a central axis of the assist pinion shaft, the first portion, and the second portion, a first distance from an end surface of the first portion on the other side in the second direction to a tip of the housing end portion located on the first portion side with respect to the central axis of the assist pinion shaft, a second distance from an end face of the second portion on the other side in the second direction to a tip of the housing end portion located on the second portion side with respect to the central axis of the assist pinion shaft, a cover member for covering the opening is provided at the housing end of the housing, the lid member includes a lid main body portion that covers the opening, and an annular protruding portion that protrudes from a peripheral edge portion of the lid main body portion to one side in the second direction, the protruding portion being disposed on an inner peripheral side of the housing end portion, When viewed from the first direction, an end of the protrusion on one side in the second direction intersects with an end face of the assist pinion shaft on the other side in the second direction. Electric power steering device.

3. When viewed from the first direction, an end of the protrusion on one side in the second direction intersects with an end face of the assist pinion shaft on the other side in the second direction.

2. The electric power steering device according to claim 1.

4. A circumferentially extending annular O-ring is provided between the outer peripheral surface of the protrusion and the housing end. The electric power steering device according to any one of claims 1 to 3.

5. The worm shaft is located on the opposite side of the rack shaft across the assist pinion shaft. The electric power steering device according to any one of claims 1 to 4.

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