Worm reduction gear equipped electric motor and electric power steering device

Abstract

To provide an electric motor with a worm speed reducer and an electric power steering system capable of alleviating an interference sound caused by a worm gear and a worm shaft.SOLUTION: An electric motor with a worm speed reducer and an electric power steering system include: a worm gear; a first housing that rotatably supports the worm gear; a worm shaft; a second housing that rotatably supports the worm shaft; an elastic member interposed between the first housing and the second housing; and a pin that couples a second region of the second housing swingably to a first region of the first housing. When seen from a third direction intersecting both a first direction and a second direction, a meshing part of the worm gear and worm shaft are aligned with the pin in the first direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an electric motor with a worm reduction gear and an electric power steering device. [Background technology]

[0002] The electric power steering device of Patent Document 1 includes a speed reduction mechanism, which includes a worm shaft and a worm wheel. The worm shaft meshes with the worm wheel, and the worm wheel also rotates when the worm shaft is driven to rotate by a motor. The worm wheel is housed in a first housing, and the worm shaft is housed in a second housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-192787 A Summary of the Invention [Problem to be solved by the invention]

[0004] The first housing is fixed to the second housing, and the first housing and the second housing are prevented from moving relative to each other. Specifically, the first housing is provided with a first opening through which the worm wheel is exposed, and the second housing is provided with a second opening through which the worm shaft is exposed. Since the peripheral edge of the first opening and the peripheral edge of the second opening are directly fixed to each other, the second housing is prevented from moving relative to the first housing. Therefore, the electric power steering device of Patent Document 1 cannot suppress backlash between the worm shaft and the worm wheel or interference noise between the teeth of each worm shaft and the worm wheel.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an electric motor with a worm reduction gear and an electric power steering device that are capable of further reducing interference noise between the worm wheel and the worm shaft. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, an electric motor with a worm reducer or an electric power steering device according to one embodiment includes a worm wheel rotatable around a central axis extending in a first direction, a first housing that accommodates the worm wheel and rotatably supports the worm wheel, a worm shaft rotatable around a central axis extending in a second direction intersecting the first direction and meshing with the worm wheel, a second housing that accommodates the worm shaft and rotatably supports the worm shaft, a rotor provided on the worm shaft, a stator disposed opposite to an outer periphery of the rotor and attached to the second housing, an elastic member disposed between the first housing and the second housing, and a pin that swingably connects a second portion of the second housing to a first portion of the first housing, and when viewed from a third direction intersecting both the first direction and the second direction, the meshing portions of the worm wheel and the worm shaft and the pin are aligned in the first direction.

[0007] As described above, in the electric power steering device of Patent Document 1, the peripheral portion of the first housing that houses the worm wheel and the peripheral portion of the second housing that houses the worm shaft are directly fixed to each other, and the second housing is prevented from moving relative to the first housing. Therefore, the electric power steering device of Patent Document 1 cannot suppress backlash between the worm shaft and the worm wheel or interference noise between the teeth of each worm shaft and worm wheel.

[0008] In contrast, in the electric motor with a worm reduction gear according to the present disclosure, the second portion of the second housing is swingably connected to the first portion of the first housing via a pin. Furthermore, since an elastic member is sandwiched between the first and second housings, the second housing is in a so-called floating state with respect to the first housing.

[0009] When the worm shaft is rotated while meshing with the worm wheel, the distance (backlash) between the central axes of the shaft teeth portion and the wheel teeth portion constantly varies. For example, when the worm shaft receives a force from the worm wheel toward the other side in the second direction due to the rotation of the worm shaft, the portion of the worm shaft below the central axis (the worm wheel side) receives the force toward the other side in the second direction. Then, when the axial center of the central axis of the worm shaft is taken as the reference, a force is applied to the worm shaft in, for example, a counterclockwise direction. Then, the second housing swings in the counterclockwise direction around the pin.

[0010] In this way, when the distance (backlash) between the central axes of the shaft teeth portion and the wheel teeth portion varies and a clockwise or counterclockwise force is applied to the worm shaft, the second housing oscillates relative to the first housing according to the force without resisting the force. This makes it possible to make the radial distance (backlash) between the central axes of the shaft teeth portion and the wheel teeth portion more uniform, and further reduces interference noise between the worm wheel and worm shaft.

[0011] In a preferred embodiment, the first portion of the first housing is a protrusion provided on one side and the other side of the worm wheel in the first direction and protruding in the third direction, and the second portion of the second housing is a protrusion provided on one side and the other side of the worm shaft in the first direction and protruding in the third direction.

[0012] Therefore, the second housing can be more stably supported on the first housing so as to be able to swing, compared to a case in which the protrusion and the projection are provided on only one side in the first direction, which makes it possible to further reduce interference noise between the worm wheel and the worm shaft.

[0013] In a preferred embodiment, the first portion is provided with a first through hole into which the pin fits, and the second portion is provided with a second through hole into which the pin fits, one of the first through hole and the second through hole is a circular hole in which the pin can rotate relative to the through hole, and the other of the first through hole and the second through hole is an irregular hole in which the pin cannot rotate relative to the through hole, and the pin has a columnar portion that fits into the circular hole and an irregular columnar portion that fits into the irregular hole. In this specification, the term "irregular hole" broadly means a hole whose cross section has a shape other than a circle (for example, a polygon or an ellipse). In other words, a hole other than a circular hole is an irregular hole. In addition, the term "irregular columnar portion" broadly means a columnar portion whose cross section has a shape other than a circle (for example, a polygon or an ellipse). In other words, a columnar portion other than a circular hole is an irregular columnar portion.

[0014] According to this, the second housing can be supported to be swingable on the first housing by using a pin having a simple structure. A specific description will be given below. The pin has an irregular columnar portion and a cylindrical portion. The first through hole of the protruding portion is an irregular hole into which the irregular columnar portion fits, and the second through hole of the protruding portion is a circular hole into which the cylindrical portion fits. Therefore, the second housing can be supported to be swingable on the first housing by a simple action of fitting the pin into the first through hole and the second through hole.

[0015] As a desirable aspect, when the pin is fitted into the first through hole and the second through hole, a first center of the cylindrical portion is shifted to one side or the other side in the third direction relative to a second center, which is the center in the third direction of the irregularly shaped cylindrical portion.

[0016] The distance (backlash) between the central axes of the shaft teeth portion and the wheel teeth portion can be adjusted by the pin. For example, when the distance between the central axes of the shaft teeth portion and the wheel teeth portion is small, the pin can be used to increase the heightwise distance between the second housing and the first housing, thereby increasing the distance between the central axes of the shaft teeth portion and the wheel teeth portion. Effect of the Invention

[0017] According to the present disclosure, there is provided an electric motor with a worm reduction gear and an electric power steering device that are capable of further reducing interference noise between the worm wheel and the worm shaft. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of an electric power steering device according to an embodiment. [Diagram 2] FIG. 2 is a schematic perspective view of the electric motor with a worm reduction gear according to the embodiment, as viewed from the output shaft side of the first steering shaft. [Diagram 3] FIG. 3 is a schematic perspective view of the worm reduction gear equipped electric motor according to the embodiment, as viewed from the input shaft side of the first steering shaft. [Figure 4] FIG. 4 is an exploded perspective view of FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line V-V in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is an exploded perspective view showing a first portion of the first housing, a second portion of the second housing, and a pin. [Figure 8] FIG. 8 is an enlarged perspective view of the pin of FIG. [Figure 9] FIG. 9 is a cross-sectional view corresponding to FIG. 6, showing a state in which the Y1 side of the second housing is lowered relative to the Y2 side. [Figure 10]FIG. 10 is a cross-sectional view corresponding to FIG. 6, showing a state in which the Y2 side of the second housing is lowered relative to the Y1 side. [Figure 11] FIG. 11 is a perspective view showing another example of the pin. [Figure 12] FIG. 12 is a perspective view showing still another example of the pin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A detailed description of the embodiment of the present invention will be given with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. The components described below can be appropriately combined. The same reference numerals are used for parts with the same structure, and the description is omitted. In the three-dimensional coordinate system, the X direction indicates the front-rear direction of the vehicle body, the Y direction indicates the width direction of the vehicle, and the Z direction indicates the up-down direction. Furthermore, the X1 side indicates the output shaft side of the first steering shaft 82, and the X2 side indicates the input shaft side. The Y1 side indicates the left side in the width direction of the vehicle, and the Y2 side indicates the right side. The Z1 side indicates the upper side, and the Z2 side indicates the lower side.

[0020] In the following description, the "first direction" refers to the axial direction of the central axis AX1 of the worm wheel 11, and the "second direction" refers to the axial direction of the central axis AX2 of the worm shafts 12, 12A. The "second direction" intersects with the "first direction." Furthermore, the "third direction" refers to a direction that intersects with both the "first direction" and the "second direction."

[0021] Here, in the following embodiment, for ease of understanding, the X direction coincides with the first direction, the Y direction coincides with the second direction, and the Z direction coincides with the third direction. The X1 side is also referred to as one side of the first direction, the X2 side as the other side of the first direction, the Y1 side as one side of the second direction, the Y2 side as the other side of the second direction, the Z1 side as one side of the third direction, and the Z2 side as the other side of the third direction. However, in the present invention, the "first direction" is not limited to the "X direction", the "second direction" is not limited to the "Y direction", and the "third direction" is not limited to the "Z direction".

[0022] Hereinafter, an embodiment will be described. FIG. 1 is a schematic diagram of an electric power steering device according to an embodiment. FIG. 2 is a schematic perspective view of an electric motor with a worm reduction gear according to an embodiment, as viewed from the output shaft side of a first steering shaft. FIG. 3 is a schematic perspective view of an electric motor with a worm reduction gear according to an embodiment, as viewed from the input shaft side of a first steering shaft. FIG. 4 is an exploded perspective view of FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 2. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 2. FIG. 7 is an exploded perspective view showing a first portion of a first housing, a second portion of a second housing, and a pin. FIG. 8 is an enlarged perspective view of the pin in FIG. 7. FIG. 9 is a cross-sectional view corresponding to FIG. 6, showing a state in which the Y1 side of the second housing is lowered relative to the Y2 side. FIG. 10 is a cross-sectional view corresponding to FIG. 6, showing a state in which the Y2 side of the second housing is lowered relative to the Y1 side.

[0023] 1, the first steering shaft 82 includes an input shaft 82a and an output shaft 82b. One end of the input shaft 82a is connected to the steering wheel 81, and the other end of the input shaft 82a is connected to the output shaft 82b. One end of the output shaft 82b is connected to the input shaft 82a, and the other end of the output shaft 82b is connected to the first universal joint 84.

[0024] 1, the second steering shaft 85 connects the first universal joint 84 and the second universal joint 86. One end of the second steering shaft 85 is connected to the first universal joint 84, and the other end of the second steering shaft 85 is connected to the second universal joint 86. One end of the third steering shaft 87 is connected to the second universal joint 86, and the other end of the third steering shaft 87 is connected to a steering gear 88.

[0025] As shown in Fig. 1, the steering gear 88 includes a pinion 88a and a rack 88b. The pinion 88a is connected to a third steering shaft 87. The rack 88b meshes with the pinion 88a. The steering gear 88 converts the rotational motion transmitted to the pinion 88a into linear motion by the rack 88b. The rack 88b is connected to a tie rod 89. The angle of the wheels changes as the rack 88b moves.

[0026] 1, the steering force assist mechanism 83 includes a worm reduction motor 100. The worm reduction motor 100 applies an auxiliary steering torque to the output shaft 82b. The worm reduction motor 100 will be described in detail later.

[0027] As shown in Fig. 1, the electric power steering device 80 includes an electric motor 100 with a worm reduction gear, an ECU (Electronic Control Unit) 90, a torque sensor 94, and a vehicle speed sensor 95. The electric motor 100 with a worm reduction gear, the torque sensor 94, and the vehicle speed sensor 95 are electrically connected to the ECU 90. The torque sensor 94 outputs the steering torque transmitted to the input shaft 82a to the ECU 90 by CAN (Controller Area Network) communication. The vehicle speed sensor 95 detects the traveling speed (vehicle speed) of the vehicle body on which the electric power steering device 80 is mounted. The vehicle speed sensor 95 is provided on the vehicle body, and outputs the vehicle speed to the ECU 90 by CAN communication.

[0028] The ECU 90 controls the operation of the first motor section 3 and the second motor section 4 (see FIG. 2) of the electric motor 100 with a worm reduction gear. The ECU 90 acquires signals from a torque sensor 94 and a vehicle speed sensor 95. When an ignition switch 98 is on, the ECU 90 is supplied with power from a power supply device 99 (for example, a battery mounted on the vehicle). The ECU 90 calculates an auxiliary steering command value based on the steering torque and the vehicle speed. The ECU 90 adjusts the value of the power supplied to the first motor section 3 and the second motor section 4 based on the auxiliary steering command value. The ECU 90 acquires information on induced voltages from the first motor section 3 and the second motor section 4 or information output from resolvers or the like provided in the first motor section 3 and the second motor section 4. The ECU 90 controls the first motor section 3 and the second motor section 4, thereby reducing the force required to operate the steering wheel 81.

[0029] As shown in Fig. 2 and Fig. 3, the electric motor 100 with a worm reduction gear includes a first structure 110, a second structure 120, an elastic member 5, and a pin 300. The first structure 110, the second structure 120, and the elastic member 5 are arranged in the vertical direction. The first structure 110 is located on the lower side (Z2 side), the elastic member 5 is arranged on the first structure 110, and the second structure 120 is arranged above the first structure 110 and the elastic member 5. In other words, the first structure 110 and the second structure 120 sandwich the elastic member 5 from above and below. The worm wheel 11 and the worm shaft 12 form the worm reduction gear 1 (see Fig. 3).

[0030] As shown in FIG. 2, FIG. 3, FIG. 4, and FIG. 5, the first structure 110 has a first housing 21 and a worm wheel 11. The first housing 21 includes a main body 211 and a cover body 212, and houses the worm wheel 11. The main body 211 is located on the X1 side in the front-rear direction (X direction), and the cover body 212 covers an opening on the X2 side of the main body 211. The worm wheel 11 extends in the first direction. In other words, the worm wheel 11 extends in the axial direction of the central axis AX1. The worm wheel 11 is rotatable in the axial direction around the central axis AX1. In addition, as shown in FIG. 4, the first housing 21 has a first opening 213 to which the worm wheel 11 is exposed, and a peripheral portion 213a of the first opening 213.

[0031] As shown in FIG. 5, the main body 211 has a first peripheral surface portion 211a, a rear wall surface portion 211b, a second peripheral surface portion 211c, a flange 211d, a disk portion 211e, a spline shaft 211f, and a protrusion portion 211g (first portion). The first peripheral surface portion 211a is a cylindrical surface extending in a circumferential direction around a central axis AX1. The rear wall surface portion 211b extends radially inward from an end of the first peripheral surface portion 211a on the X1 side. The second peripheral surface portion 211c is a cylindrical surface extending in a circumferential direction. The second peripheral surface portion 211c extends from an end of the rear wall surface portion 211b on the radially inner side toward the X1 side. The disk portion 211e is fitted to the inner peripheral side of the second peripheral surface portion 211c. The flange 211d extends radially inward from the end of the second circumferential surface portion 211c on the X1 side. As shown in Fig. 5, the spline shaft 211f is rotatably supported by the disk portion 211e, and the spline shaft 211f is connected to the worm wheel 11. The spline shaft 211f is integral with a protruding portion 212d, which will be described later. The output shaft 82b of the first steering shaft 82 is connected to the spline shaft 211f, and the input shaft 82a of the first steering shaft 82 is connected to the protruding portion 212d.

[0032] As shown in FIG. 5, the cover body part 212 has a front part 212a, a cylindrical part 212b, a plate part 212c, and a protruding part 212d. The front part 212a extends radially inward. The peripheral edge part of the front part 212a faces the X2 side end of the first peripheral part 211a. The cylindrical part 212b extends cylindrically from the radially inner end of the front part 212a toward the X1 side. The plate part 212c is fitted to the inner periphery side of the cylindrical part 212b. Note that, as shown in FIG. 3, the cylindrical protruding part 212d protrudes toward the X2 side from the plate part 212c.

[0033] 5, the worm wheel 11 is disposed between the plate portion 212c and the disk portion 211e. The worm wheel 11 includes a core metal 11a located in the radial center and a wheel tooth portion 11b located on the outer circumferential side of the core metal 11a. The core metal 11a is formed to be thicker in the X direction than the wheel tooth portion 11b. A spline shaft 211f is connected to the core metal 11a.

[0034] 4, a recessed groove 210 is provided in an upper surface 21a of the first housing 21. The upper surface 21a also forms a peripheral portion 213a of the first opening 213. An elastic member 5 is inserted into the recessed groove 210. The elastic member 5 is made of, for example, rubber.

[0035] 4, the top surface 21a of the first housing 21 includes a flat portion 21b and curved portions 21c and 21d. A groove 210 is provided in the flat portion 21b and the curved portions 21c and 21d. The curved portions 21c and 21d are curved and convex toward the Z1 side (upward). The curved portion 21c is a portion of the top surface 21a on the X2 side, and the curved portion 21d is a portion of the top surface 21a on the X1 side.

[0036] Next, the second structure 120 will be described. As shown in Fig. 2, the second structure 120 includes a second housing 22, a worm shaft 12, a first motor unit 3, and a second motor unit 4. A central axis AX2 of the worm shaft 12 extends in the Y direction (second direction).

[0037] As shown in FIG. 2 and FIG. 3, the second housing 22 has a lower frame portion 221, a bearing fixing portion 222, a flange 223, and a cover 23. The lower frame portion 221 has a flat portion 221a, a curved portion 221b, and a curved portion 221c. The curved portion 221b has a curved shape that is convex toward the upper side (Z1 side). The curved portion 221b connects the flat portion 221a on the Y1 side and the flat portion 221a on the Y2 side on the X2 side of the lower frame portion 221. The Z direction thickness of the curved portion 221b is thicker than the Z direction thickness of the curved portion 221c. The curved portion 221c connects the flat portion 221a on the Y1 side and the flat portion 221a on the Y2 side on the X1 side of the lower frame portion 221. As shown in FIG. 4, the bearing fixing portion 222 is provided on the upper side of the lower frame portion 221. The bearing fixing portion 222 is provided on each of the Y1 side and the Y2 side. When viewed from the Y direction, the bearing fixing portion 222 is annular. The bearing 130 is fitted to the inner periphery side of the bearing fixing portion 222. The bearing 130 has an inner ring, an outer ring, and rolling elements. The shaft portion (shaft portion) 12a of the worm shaft 12 is fitted to the inner periphery side of the inner ring of the bearing 130.

[0038] Therefore, the Y1 side and the Y2 side of the worm shaft 12 are rotatably supported by the second housing 22 via the bearing 130. As shown in FIG. 4, the flange 223 extends in the Z direction and the Y direction. That is, the flange 223 extends upward (Z1 side) from the upper end of the bearing fixing part 222. The flange 223 connects the upper end of the bearing fixing part 222 on the Y1 side to the upper end of the bearing fixing part 222 on the Y2 side. The cover 23 shown by dotted hatching covers the worm shaft 12. The cover 23 prevents foreign matter such as metal powder from adhering to the worm shaft 12. As shown in FIG. 4, the lower frame part 221 of the second housing 22 has a second opening 224 from which the worm shaft 12 is exposed and a peripheral part 224a of the second opening 224.

[0039] As shown in FIG. 6, the worm shaft 12 has a shaft portion 12a, a shaft tooth portion 12b, a large diameter portion 12c, and a tapered portion 12d. The worm shaft 12 extends in the second direction. In other words, the worm shaft 12 extends in the axial direction of the central axis AX2. As described above, the shaft portion 12a is rotatably supported by the second housing 22 via the bearing 130. The large diameter portion 12c is located inside the shaft portion 12a in the axial direction. In other words, the large diameter portion 12c is provided on the center side of the axial direction of the worm shaft 12 with respect to the shaft portion 12a. The outer peripheral surface of the large diameter portion 12c is a cylindrical surface along the circumferential direction around the central axis AX2. The diameter of the large diameter portion 12c is larger than the diameter of the shaft portion 12a. The tapered portion 12d is located inside the large diameter portion 12c in the axial direction. The diameter of the tapered portion 12d decreases toward the inside in the axial direction (toward the center in the axial direction of the worm shaft 12). In other words, in a cross section including the central axis AX2, the outer circumferential surface of the tapered portion 12d approaches the central axis AX2 toward the center in the axial direction of the worm shaft 12. In addition, a shaft tooth portion 12b is provided between the tapered portion 12d on the Y1 side and the tapered portion 12d on the Y2 side. The shaft tooth portion 12b of the worm shaft 12 meshes with the wheel tooth portion 11b of the worm wheel 11. That is, when the worm shaft 12 rotates in a direction around the central axis AX2, the worm wheel 11 rotates in a direction around the central axis AX1.

[0040] The large diameter portion 12c and the tapered portion 12d constitute the rotor 250. The rotor 250 is manufactured by stacking thin plates such as electromagnetic steel plates and cold-rolled steel plates and fixing them to the worm shaft 12 by caulking or the like. When a permanent magnet is used for the rotor, as in a permanent magnet synchronous motor, an opening for inserting a magnet can be provided in advance in the thin plates used to form the rotor 250. By stacking the thin plates, an insertion hole for inserting a magnet is formed in the aforementioned opening for inserting a magnet. The rotor 250 can be manufactured by inserting a permanent magnet into this insertion hole. Alternatively, the rotor may be manufactured by sintering magnetic powder.

[0041] As shown in Fig. 4, the first motor section 3 has a stator 31 and a support plate 38. The stators 31 are arranged in pairs on the X1 side and the X2 side. The stator 31 is formed by winding coils 240 (see Fig. 5) around teeth 33.

[0042] As shown in Fig. 4, the support plate 38 is provided on each of the X1 side and the X2 side. The support plate 38 includes an upper end flange 38a, an arcuate portion 38b, and a lower end flange 38c. The stator 31 is fixed to the inner peripheral surface of the arcuate portion 38b. The rotor 250 described above is disposed opposite the inner peripheral side of the stator 31.

[0043] 5, the second motor section 4 has a stator 41 and a support plate 37. The stators 41 are arranged in pairs on the X1 side and the X2 side with the central axis AX2 in between. In other words, in a cross section including the central axis AX2, the stator 41 on the X1 side and the stator 41 on the X2 side are symmetrical with respect to a straight line that passes through the central axis AX2 and extends in the Z direction.

[0044] The stator 41 has teeth 43 and coils 240. The coils 240 are wound around the teeth 43 to form the stator 41.

[0045] The support plate 37 is provided on each of the X1 side and the X2 side. The support plate 37 includes an upper end flange 37a, an arcuate portion 37b, and a lower end flange 37c. The stator 41 is fixed to the inner peripheral surface of the arcuate portion 37b. The rotor 250 described above is disposed opposite the inner peripheral side of the stator 41.

[0046] Next, a support structure for the first structure 110 and the second structure 120 will be described. As shown in FIG. 4, a protrusion (first portion) 211g is provided at the top of each of the curved portions 21c, 21d of the first housing 21. In other words, the protrusion (first portion) 211g protrudes upward (Z1 side) from the top located at the center of the curved portions 21c, 21d in the Y direction. As shown in an enlarged view in FIG. 7, the protrusion 211g has a plate shape and is provided with a first through hole 211h. The first through hole 211h has a generally elliptical shape that is elongated in the vertical direction (Z direction). The first through hole 211h is an irregularly shaped hole.

[0047] 5 and 7, a protrusion (second portion) 221d is provided at the top of each of the curved portions 221b and 221c of the second housing 22. In other words, the protrusion (second portion) 221d protrudes upward (Z1 side) from the top of the curved portions 221b and 221c located at the center in the Y direction. The protrusion 221d has a semicircular shape convex upward when viewed from the X direction, and a second through hole 221e is provided. The second through hole 221e is circular when viewed from the X direction. The second through hole 221e is a circular hole. The protrusion (first portion) 211g and the protrusion (second portion) 221d are provided at the center in the Y direction of the first housing 21 and the second housing 22. 6, the meshing portion 200 where the wheel teeth 11b of the worm wheel 11 mesh with the shaft teeth 12b of the worm shaft 12 is also provided at the center in the Y direction of the first housing 21 and the second housing 22. Therefore, when viewed from the Z direction (up-down direction, third direction), the meshing portion 200 and the pin 300 are aligned in the X direction (first direction).

[0048] As shown in FIG. 6, the gap between the second structure 120 and the first structure 110 in the Z direction (vertical direction) is approximately the same on the Y1 side and the Y2 side. Specifically, at the Y1 side end and the Y2 side end, the lower end 221g of the second structure 120 is the peripheral portion 224a of the second opening 224, and the upper end 221f of the first structure 110 is the peripheral portion 213a of the first opening 213. As shown in FIG. 6, at the Y1 side end and the Y2 side end, a gap is provided between the lower end 221g of the second structure 120 and the upper end 221f of the first structure 110, which is separated by a distance D1 in the Z direction (vertical direction). In this way, when the worm shaft 12 is not rotating, the gap between the second structure 120 and the first structure 110 in the Z direction (vertical direction) has approximately the same distance D1 at the Y1 side end and the Y2 side end.

[0049] Here, as shown in FIG. 7 and FIG. 8, the pin 300 has a cylindrical portion 301, a deformed columnar portion 302, and a flange portion 303. The cylindrical portion 301 has a first center Z10 and extends along the first center Z10. The cylindrical portion 301 has a cylindrical outer peripheral surface 301a extending along the circumferential direction of the first center Z10. The tip surface 301b of the cylindrical portion 301 is a flat surface perpendicular to the first center Z10. The deformed columnar portion 302 has a second center Z20 and extends along the second center Z20. The second center Z20 is located on the same axis as the first center Z10. The deformed columnar portion 302 is adjacent to the cylindrical portion 301 on the X2 side. The deformed columnar portion 302 has a larger diameter in the Y direction and the Z direction than the cylindrical portion 301. The irregular columnar portion 302 is a generally elliptical column that is elongated in the vertical direction (Z direction). An annular tip surface 302b located on the X1 side of the irregular columnar portion 302 is exposed. The tip surface 302b is a flat surface perpendicular to the second center Z20. The flange portion 303 is adjacent to the irregular columnar portion 302 on the X2 side. The flange portion 303 has a larger diameter in the Y direction and the Z direction than the irregular columnar portion 302. The flange portion 303 is a cylinder having a cylindrical surface 303a. An annular tip surface 303b located on the X1 side of the flange portion 303 is exposed. The tip surface 303b is a flat surface perpendicular to the first center Z10 and the second center Z20.

[0050] As shown in FIG. 7, the columnar portion 301 of the pin 300 fits into the second through hole 221e of the protruding portion 221d. The second through hole 221e is a circular hole. Therefore, when the columnar portion 301 is fitted into the second through hole 221e, the columnar portion 301 and the second through hole 221e can rotate relative to each other. The irregular column portion 302 of the pin 300 fits into the first through hole 211h of the protruding portion (first portion) 211g. The first through hole 211h is an irregular hole. Therefore, when the irregular column portion 302 is fitted into the first through hole 211h, the irregular column portion 302 cannot rotate with respect to the first through hole 211h.

[0051] As described above, the second center Z20 of the pin 300 is located on the same axis as the first center Z10. Therefore, when the pin 300 is fitted into the first through hole 211h and the second through hole 221e, the center in the Z direction of the first through hole 211h and the center of the second through hole 221e are arranged on the same axis. As shown in FIG. 5, the first through hole 211h and the second through hole 221e are also provided for the protrusion 211g and the protrusion 221d on the X2 side, and the pin 300 is fitted into the first through hole 211h and the second through hole 221e. Therefore, the support structure of the second structure 120 and the first structure 110 on the X2 side is the same as that on the X1 side.

[0052] Next, the manner in which the second structure 120 swings relative to the first structure 110 will be described with reference to Fig. 9 and Fig. 10. With the elastic member 5 sandwiched between the second structure 120 and the first structure 110, the protrusion (first portion) 211g and the protrusion (second portion) 221d are swingably connected via the pin 300, so that the second structure 120 is assembled to the first structure 110. At this time, the elastic member 5 is elastically deformable by the second structure 120 and the first structure 110, and the second structure 120 is in a so-called floating state relative to the first structure 110. The center of swing of the second structure 120 relative to the first structure 110 is the first center Z10 (second center Z20).

[0053] Here, when the electric motor 100 with a worm reduction gear is viewed from the X1 side toward the X2 side as shown in FIG. 9, the engagement between the worm wheel 11 and the worm shaft 12 may apply a force to the second structure 120 to swing it in the counterclockwise direction. In this case, the part on the Y2 side of the second structure 120 moves toward the upper side (Z1 side) as shown by the arrow P1, and the part on the Y1 side of the second structure 120 moves toward the lower side (Z2 side) as shown by the arrow P2. Then, on the Y2 side, the upper end 221f of the first structure 110 and the lower end 221g of the second structure 120 are vertically separated by a distance D2. Also, on the Y1 side, the upper end 221f of the first structure 110 and the lower end 221g of the second structure 120 come into contact with each other.

[0054] 10, when the electric motor 100 with a worm reducer is viewed from the X1 side toward the X2 side, a force that swings the second structure 120 in a clockwise direction may be applied due to the meshing of the worm wheel 11 and the worm shaft 12. In this case, the part on the Y2 side of the second structure 120 moves downward (to the Z2 side) as shown by the arrow P3, and the part on the Y1 side of the second structure 120 moves upward (to the Z1 side) as shown by the arrow P4. Then, on the Y1 side, the upper end 221f of the first structure 110 and the lower end 221g of the second structure 120 are vertically separated by a distance D3. On the Y2 side, the upper end 221f of the first structure 110 and the lower end 221g of the second structure 120 come into contact with each other.

[0055] Next, other aspects of the pin will be described. FIG. 11 is a perspective view showing another example of the pin. FIG. 12 is a perspective view showing yet another example of the pin. The pin 310 shown in FIG. 11 differs from the pin 300 shown in FIG. 8 in the vertical (Z-direction) position of the cylindrical portion 301. That is, in the pin 310, the cylindrical portion 301 has a first center Z11 and extends along the first center Z11. The irregular column portion 302 has a second center Z21 passing through the center in the Z direction and extends along the second center Z21. The first center Z11 is positioned at a distance D10 shifted from the second center Z21 to the Z1 side (upper side, one side in the third direction). In other words, the second center Z21 is positioned at a distance D10 shifted from the first center Z11 to the Z2 side (lower side).

[0056] The pin 320 shown in Fig. 12 differs from the pin 300 shown in Fig. 8 in the position of the columnar portion 301 in the up-down direction (Z direction). That is, in the pin 320, the columnar portion 301 has a first center Z12 and extends along the first center Z12. The irregular shaped columnar portion 302 has a second center Z22 passing through the center in the Z direction and extends along the second center Z22. The first center Z12 is positioned at a distance D20 shifted toward the Z2 side (lower side, the other side in the third direction) from the second center Z22. In other words, the second center Z22 is positioned at a distance D20 shifted toward the Z1 side (upper side) from the first center Z12.

[0057] As described above, the electric motor 100 with a worm reducer includes the worm wheel 11 rotatable around a central axis AX1 extending in the X direction (first direction), the first housing 21 that accommodates the worm wheel 11 and rotatably supports the worm wheel 11, the worm shaft 12 that is rotatable around a central axis AX2 extending in the Y direction (second direction) and meshes with the worm wheel 11, the second housing 22 that accommodates the worm shaft 12 and rotatably supports the worm shaft 12, the elastic member 5 arranged between the first housing 21 and the second housing 22, and the pins 300, 310, 320 that swingably connect the protrusion 221d (second portion) of the second housing 22 to the protrusion 211g (first portion) of the first housing 21. When viewed from the Z direction (third direction), the meshing portion 200 of the worm wheel 11 and the worm shaft 12 and the pins 300, 310, 320 are aligned in the X direction (first direction).

[0058] In the electric power steering device of the above-mentioned Patent Document 1, the peripheral edge of the first housing that houses the worm wheel and the peripheral edge of the second housing that houses the worm shaft are directly fixed to each other, and the second housing is prevented from moving relative to the first housing. Therefore, the electric power steering device of Patent Document 1 cannot suppress backlash between the worm shaft and the worm wheel or interference noise between the teeth of each worm shaft and worm wheel.

[0059] In contrast, in the electric motor 100 with a worm reduction gear according to this embodiment, the protruding portion 221d (second portion) of the second housing 22 is swingably connected to the protruding portion 211g (first portion) of the first housing 21 via pins 300, 310, and 320. Furthermore, since an elastic member is sandwiched between the first housing 21 and the second housing 22, the second housing 22 is in a so-called floating state with respect to the first housing 21.

[0060] When the worm shaft 12 is rotated in a state where the shaft teeth 12b of the worm shaft 12 mesh with the wheel teeth 11b of the worm wheel 11, the distance (backlash) between the central axes of the shaft teeth 12b and the wheel teeth 11b always varies. For example, when the shaft teeth 12b receives a force from the wheel teeth 11b toward the Y2 side due to the rotation of the worm shaft 12, the portion of the worm shaft 12 below the central axis AX2 receives the force toward the Y2 side, as shown in FIG. 9. If the center of the axial direction of the central axis AX2 of the worm shaft 12 is the center C, a counterclockwise force is applied with the center C as a reference. Then, as described above, the second housing 22 swings in the counterclockwise direction around the pins 300, 310, and 320.

[0061] In this way, when the distance (backlash) between the central axes of the shaft tooth portion 12b and the wheel tooth portion 11b varies and a clockwise or counterclockwise force is applied to the worm shaft 12, the second housing 22 oscillates relative to the first housing 21 in accordance with the force without resisting the force. This makes it possible to make the distance (backlash) between the central axes of the shaft tooth portion 12b and the wheel tooth portion 11b more uniform, and makes it possible to further reduce interference noise between the worm wheel 11 and the worm shaft 12.

[0062] The protrusions 211g (first portion) of the first housing 21 are provided on the X1 side (one side) and the X2 side (the other side) in the X direction (first direction) with the worm wheel 11 in between, and protrude in the Z direction (third direction). The protrusions 221d (second portion) of the second housing 22 are provided on the X1 side (one side) and the X2 side (the other side) in the X direction (first direction) with the worm shaft 12 in between, and protrude in the Z direction (third direction).

[0063] Therefore, the second housing 22 can be more stably supported to be swingable on the first housing 21 than when the protrusion 211g (first portion) and the protrusion 221d (second portion) are provided on only one side in the X direction (first direction). This makes it possible to further reduce interference noise between the worm wheel 11 and the worm shaft 12.

[0064] The first through hole 211h into which the pins 300, 310, 320 fit is provided in the protruding portion 211g, which is the first portion, and the second through hole 221e into which the pins 300, 310, 320 fit is provided in the protruding portion 221d, which is the second portion. The second through hole 221e is a circular hole into which the pins 300, 310, 320 can rotate relative to the through hole. The first through hole 211h is an irregular hole into which the pins 300, 310, 320 cannot rotate relative to the through hole. The pins 300, 310, 320 have a cylindrical portion 301 that fits into the circular hole and an irregular column portion 302 that fits into the irregular hole.

[0065] According to this, the second housing 22 can be supported to the first housing 21 so as to be able to swing using the pins 300, 310, 320 having a simple structure. A specific description will be given below. The pins 300, 310, 320 have an irregular columnar portion 302 and a cylindrical portion 301. The first through hole 211h of the protruding portion 211g is an irregular hole into which the irregular columnar portion 302 fits, and the second through hole 221e of the protruding portion 221d is a circular hole into which the cylindrical portion 301 fits. Therefore, the second housing 22 can be supported to the first housing 21 so as to be able to swing by fitting the pins 300, 310, 320 into the first through hole 211h and the second through hole 221e.

[0066] When the pins 310, 320 are fitted into the first through hole 211h and the second through hole 221e, the first centers Z11, Z12 in the cylindrical portion 301 are shifted toward the Z1 side (upper side, one side) or the Z2 side (lower side, the other side) in the Z direction (third direction) relative to the second centers Z21, Z22.

[0067] Specifically, in the pin 310, the first center Z11 is shifted toward the Z1 side (upper side, one side) in the Z direction (third direction) with respect to the second center Z21. Therefore, in a state where the pin 310 is fitted into the first through hole 211h and the second through hole 221e, the relative position of the second housing 22 in the Z direction (third direction) with respect to the first housing 21 is disposed on the Z1 side (upper side) than in a state where the pin 300 is fitted into the first through hole 211h and the second through hole 221e. This reduces the distance (backlash) between the central axes of the shaft tooth portion 12b and the wheel tooth portion 11b. In this way, when the distance (backlash) between the central axes of the shaft tooth portion 12b and the wheel tooth portion 11b is large, the pin 310 can be used to reduce the distance (backlash) between the central axes.

[0068] In addition, since the pin 320 supports the second housing 22 so that it can swing at a lower position, when the distance (backlash) between the central axes of the shaft tooth portion 12b and the wheel tooth portion 11b is small, the pin 320 can be used to increase the distance (backlash) between the central axes.

[0069] The present invention is not limited to the above-described embodiment, and can be applied to various speed reduction mechanisms of electric power steering (EPS) devices, speed reduction mechanisms of steering reaction devices in so-called steer-by-wire systems, etc. Examples of EPS devices include a so-called column-type EPS device in a steering column, a so-called pinion-type EPS device, and a so-called dual pinion-type EPS device.

[0070] The column-type EPS device applies assist power to a steering shaft rotatably supported inside a steering column. The pinion-type EPS device applies assist power to a steering pinion shaft of a steering gear unit. The dual-pinion-type EPS device applies assist power to an assist pinion shaft provided in the steering gear unit and separate from the steering pinion shaft. The reduction mechanism of the steering reaction force device in the steer-by-wire system applies a steering reaction force in accordance with the vehicle driving conditions to a steering shaft rotatably supported inside a steering column that is not mechanically connected to the steering gear unit.

[0071] In addition, in the reduction mechanism of the steering reaction force device in the steer-by-wire system, the reaction force to be applied is set to be relatively small compared to the auxiliary power in the EPS device, so that even greater effects can be expected in the form of a more compact electric motor with a worm reduction gear, which is the problem to be solved by the present application. [Explanation of symbols]

[0072] 1 Worm reducer 3 First motor section 4 Second motor section 5 Elastic member 11 Worm wheel (worm reducer) 11a Core metal 11b Wheel tooth part 12 Worm shaft (worm reducer) 12a Shaft part 12b Shaft teeth 12c Large diameter section 12d Tapered section 21 1st Housing 21a Top surface 21b Flat part 21c, 21d Curved section 22 Second Housing 23 Cover 31 Stator 33 Teeth 37 Support Plate 37a Upper flange 37b Arc section 37c Lower flange 38 Support Plate 38a Upper flange 38b Arc section 38c Lower flange 41 Stator 43 Teeth 80 Electric power steering device 81 Steering Wheel 82 First steering shaft 82a Input shaft 82b Output shaft 83 Steering force assist mechanism 84 First universal joint 85 Second steering shaft (steering shaft) 86 Second universal joint 87 Third steering shaft 88 Steering gear 88a Pinion 88b Rack 89 Tie rod 90 ECU(Electronic Control Unit) 94 Torque Sensor 95 Vehicle speed sensor 100 Worm geared motor 110 First structure 120 Second structure 130 Bearings 200 Meshing part 210 Groove 211 Main body 211a First circumferential surface part 211b Rear wall section 211c 2nd circumference part 211d flange 211e Disk Section 211f spline shaft 211g Protrusion (1st part) 211h 1st through hole 212 Lid body 212a Front part 212b Cylindrical part 212c Plate section 212d Projection part 213 First Opening 213a Periphery 221 Lower frame part 221a Flat area 221b, 221c curved section 221d Protruding part (second part) 221e 2nd through hole 221f top end 221g bottom end 222 Bearing fixing part 223 Flange 224 Second Opening 224a Periphery 240 Coil 250 rotor 300, 310, 320 pins 301 Cylinder 301a Outer surface 301b Tip surface 302 Irregular column part 303 Flange part 303a Cylindrical surface 303b Tip surface AX1, AX2 center axis Z10 1st center Z20 2nd center

Claims

1. a worm wheel rotatable around a central axis extending in a first direction; a first housing that accommodates the worm wheel and rotatably supports the worm wheel; a worm shaft that is rotatable around a central axis that extends in a second direction intersecting the first direction and that meshes with the worm wheel; a second housing that accommodates the worm shaft and rotatably supports the worm shaft; A rotor provided on the worm shaft; a stator disposed opposite an outer circumferential side of the rotor and attached to the second housing; an elastic member disposed between the first housing and the second housing; a pin that pivotally connects a second portion of the second housing to a first portion of the first housing; Equipped with When viewed from a third direction intersecting both the first direction and the second direction, The meshing portion of the worm wheel and the worm shaft and the pin are aligned in the first direction. Electric motor with worm gear reducer.

2. the first portions of the first housing are protrusions provided on one side and the other side in the first direction with the worm wheel interposed therebetween and protruding in the third direction, The second portions of the second housing are provided on one side and the other side in the first direction with the worm shaft interposed therebetween and are protruding portions protruding in the third direction.

2. An electric motor with a worm reduction gear according to claim 1.

3. The first portion is provided with a first through hole into which the pin fits, The second portion is provided with a second through hole into which the pin fits, one of the first through hole and the second through hole is a circular hole in which the pin can rotate relative to the circular through hole; the other of the first through hole and the second through hole is a special-shaped hole in which the pin cannot rotate relative to the other through hole, The pin has a cylindrical portion that fits into the circular hole and a deformed column portion that fits into the deformed hole.

3. An electric motor with a worm reduction gear according to claim 2.

4. In a state in which the pin is fitted into the first through hole and the second through hole, A first center of the cylindrical portion is shifted to one side or the other side in the third direction with respect to a second center, which is the center of the irregular shaped columnar portion in the third direction.

4. An electric motor with a worm reduction gear according to claim 3.

5. A worm reduction gear-equipped electric motor according to any one of claims 1 to 4, Electric power steering device.

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