Worm gear mechanism and electric power steering device provided with worm gear mechanism

Abstract

A worm gear mechanism (30) is provided with a grease supply part (51) that can supply, to a meshing part (34), grease which adheres to an end surface (33) of a worm wheel (32). The grease supply part (51) has a grease receiving part (60) which is provided at a position where the grease adhering to the end surface (33) of the worm wheel (32) can be contacted and the grease can be received when the worm wheel (32) rotates, and which supplies the received grease toward the meshing part (34).

Description

Worm gear mechanism and electric power steering device equipped with the worm gear mechanism

[0001] The present invention relates to an improved worm gear mechanism and an electric power steering device equipped with the worm gear mechanism.

[0002] Some steering devices are equipped with a worm gear mechanism for reducing the steering force of the steering wheel. Generally, the worm gear mechanism of a steering device includes a worm gear that rotates by the driving force generated by an electric motor, and a worm wheel that meshes with the worm gear and transmits the driving force of the electric motor to a steering rack.

[0003] Because slippage occurs on the meshing surfaces between worm gears, it is important to maintain lubrication of the meshing surfaces by applying grease to the meshing surfaces. An example of prior art for maintaining lubrication of meshing surfaces is disclosed in Patent Document 1.

[0004] A grease retaining plate with a diameter larger than the outer diameter of the worm wheel is attached to the lower end face of the worm wheel disclosed in Patent Document 1. The outer peripheral edge of the grease retaining plate is bent upward to prevent grease from leaking outward in the radial direction, and multiple ribs are formed around the periphery to engage with the worm wheel. This configuration allows grease to be retained on the meshing surfaces, maintaining lubrication of the meshing surfaces.

[0005] JP 2009-248724 A

[0006] However, when the worm gear mechanism operates, some of the grease applied to the meshing surface inevitably leaks out onto the end face of the worm wheel. Grease has a high viscosity among lubricants. The grease that leaks out from the meshing surface remains attached to the end face of the worm wheel, and this requires improvement.

[0007] An object of the present invention is to provide a worm gear mechanism and an electric power steering equipped with a worm gear mechanism that can maintain a lubricated state with grease.

[0008] First, a worm gear mechanism is provided, comprising: a worm gear that rotates by a driving force generated by a driving source; a worm wheel that meshes with the worm gear; and a grease supply unit that can supply grease adhering to the end surface of the worm wheel to the meshing portion when the meshing portion is the portion where the worm wheel and the worm gear mesh most deeply with each other when viewing the end surface of the worm wheel from a direction along the rotation axis of the worm wheel, wherein the grease supply unit is arranged at a position where it can come into contact with and receive grease adhering to the end surface of the worm wheel when the worm wheel rotates, and has a grease receiving portion that supplies the received grease towards the meshing portion.

[0009] Secondly, preferably, the worm gear mechanism described in the first aspect is provided with a housing that houses the worm gear and the worm wheel, and the grease supply portion has a support portion that supports an end of the grease receiving portion and is formed integrally with the grease receiving portion, and the support portion is superimposed on and fixed to the housing.

[0010] Third, preferably, in the worm gear mechanism according to the second aspect, the housing includes a box having an opening and a lid that closes the opening, and the support portion is fixed to the lid.

[0011] Fourth, preferably, in the worm gear mechanism described in First, the grease receiving portion has a guide end point portion closest to the meshing portion and an end face adjacent portion provided in a straight line from the guide end point portion along the end face of the worm wheel, a plane including the rotation axis of the worm wheel and the meshing portion is used as a reference plane, and the end face adjacent portion is arranged at an angle with respect to the reference plane when viewed from a direction along the rotation axis of the worm wheel.

[0012] Fifth, preferably, in the worm gear mechanism described in the first, the grease receiving portion has a grease receiving main body portion that includes a guide end point portion closest to the meshing portion and is arranged so as to stand upright relative to the end face of the worm wheel, a plane that includes the rotation axis of the worm wheel and the meshing portion is used as a reference plane, and the grease receiving main body portion includes an inclined portion that is arranged in a direction away from the reference plane, with the vertical direction of the end face of the worm wheel as a reference.

[0013] Sixth, preferably, in the worm gear mechanism according to any one of the first to fifth aspects, the grease supply portion has a weak portion that is weaker than surrounding portions of the grease supply portion.

[0014] Seventh, preferably, in the worm gear mechanism according to the sixth aspect, the weakened portion is provided at an end of the grease receiving portion or in the grease receiving portion.

[0015] Eighth, preferably, the worm gear mechanism described in First is provided with a second grease supply unit that is provided in a position where it can come into contact with grease adhering to the end face of the worm wheel when the worm wheel rotates and receive the grease, and supplies the received grease toward the meshing portion, wherein a plane including the rotation axis of the worm wheel and the meshing portion is used as a reference plane, and the grease supply unit is located on one side of the reference plane as a boundary, and the second grease supply unit is located on the other side of the reference plane as a boundary.

[0016] Ninth, in the worm gear mechanism according to the eighth, preferably, the second grease supply portion has a shape symmetrical to the grease supply portion with respect to the reference plane.

[0017] Tenth, preferably, in the worm gear mechanism described in ninth, the grease supply portion and the second grease supply portion are integrated and have an annular shape surrounding the rotation axis when viewed from a direction along the rotation axis of the worm wheel.

[0018] Eleventh, there is provided an electric power steering device comprising: a worm gear that rotates by a driving force generated by an electric motor; a worm wheel that meshes with the worm gear and transmits the driving force of the electric motor to a steering rack; and a grease supply unit that can supply grease adhering to the end surface of the worm wheel to the meshing portion when the meshing portion is the portion where the worm wheel and the worm gear mesh most deeply with each other when viewing the end surface of the worm wheel from a direction along the rotation axis of the worm wheel, wherein the grease supply unit is provided at a position where it can come into contact with and receive grease adhering to the end surface of the worm wheel when the worm wheel rotates, and has a grease receiving unit that supplies the received grease towards the meshing portion.

[0019] The present invention can provide a worm gear mechanism and an electric power steering equipped with a worm gear mechanism that can maintain a lubricated state with grease.

[0020] FIG. 3A is a schematic diagram of an electric power steering device equipped with a worm gear mechanism. FIG. 3B is an exploded perspective view of the worm gear mechanism. FIG. 3A is a view illustrating the worm wheel and worm gear as viewed from a direction along the rotation axis of the worm wheel. FIG. 3B is a view illustrating the grease supplier (grease supplier portion) as viewed from a direction along the rotation axis of the worm wheel. FIG. 3B is a perspective view of the grease supplier portion as viewed from below. FIG. 6A is a view illustrating the grease supplier portion as viewed from the side and the worm gear mechanism. FIG. 6B is a view illustrating a cross section of a grease receiver. FIG. 7 is a view illustrating the operation of the grease supplier (grease supplier portion).

[0021] <Example> An example will be described with reference to the attached drawings. Note that L indicates left, R indicates right, Up indicates top, and Dn indicates bottom.

[0022] Referring to Fig. 1, an electric power steering device 10 includes a steering mechanism 20 extending from a steering wheel 21 of a vehicle to steered wheels 29, 29 (for example, front wheels) of the vehicle, and an assist torque mechanism 11 that applies an assist torque to the steering mechanism 20.

[0023] The steering mechanism 20 connects a pinion shaft 24 to a steering wheel 21 via a steering shaft 22 and universal joints 23, 23, connects a rack shaft 26 (steering rack) to the pinion shaft 24 via a rack-and-pinion mechanism 25, and connects left and right steered wheels 29, 29 to both ends of the rack shaft 26 via left and right tie rods 27, 27 and knuckles 28, 28.

[0024] The rack and pinion mechanism 25 is made up of a pinion 24 a formed on a pinion shaft 24 and a rack 26 a formed on a rack shaft 26 .

[0025] With the above-described configuration, when the driver steers the steering wheel 21, the left and right steered wheels 29, 29 can be steered by the steering torque via the rack and pinion mechanism 25 and the left and right tie rods 27, 27.

[0026] The assist torque mechanism 11 detects the steering torque of the steering mechanism 20 applied to the steering wheel 21 with a steering torque sensor 12, generates a control signal in a control unit 13 based on a torque detection signal from the steering torque sensor 12, and generates an assist torque corresponding to the steering torque with an electric motor 14 (drive source) based on this control signal, and transmits this assist torque to the rack shaft 26 via a worm gear mechanism 30. Note that the assist torque from the worm gear mechanism 30 may also be configured to be transmitted to the pinion shaft 24.

[0027] (Worm Gear Mechanism) See Fig. 2. The worm gear mechanism 30 includes a worm gear 31 that rotates by a driving force generated by an electric motor 33 (see Fig. 1), a worm wheel 32 that meshes with the worm gear 31, and a housing 40 that houses the worm gear 31 and the worm wheel 32.

[0028] (Housing, Rotational Axis) The housing 40 includes a box 41 having an opening 41a that opens upward, and a lid 42 that closes the opening 41a of the box 41. The lid 42 is fixed to the box 41 with fastening members 43, 43 such as bolts. The shaft portion 32a of the worm wheel 32 meshes with the rack shaft 26 (see FIG. 1). The rotational axis Ax of the shaft portion 32a extends in a direction that penetrates the lid 42.

[0029] 3A , when the annular end face 33 of the worm wheel 32 is viewed from the direction along the rotation axis Ax of the worm wheel 32, the meshing portion 34 is the portion where the outer circumferential edge 33 a of the end face 33 of the worm wheel 32 and the worm gear 31 mesh most deeply with each other.

[0030] 2 to 3B, the worm gear mechanism 30 further includes a grease supplier 50 that can supply grease adhering to the end face 33 of the worm wheel 32 to the meshing portion 34. The grease supplier 50 is disposed between the lid 42 and the end face 33 of the worm wheel 32.

[0031] The grease supplier 50 is made of resin. The resin that constitutes the grease supplier 50 contains long fibers, such as glass fiber or carbon fiber. The material that constitutes the grease supplier 50 may be any type, including metal, as long as it has a predetermined rigidity. Each part that constitutes the grease supplier 50 is plate-shaped.

[0032] (First Reference Plane, Second Reference Plane) A plane including the rotation axis Ax of the worm wheel 32 and the meshing portion 34 is defined as a first reference plane P1. A plane including the rotation axis Ax and perpendicular to the first reference plane P1 is defined as a second reference plane P2.

[0033] (First grease supply portion, second grease supply portion) The grease supply body 50 includes a first grease supply portion 51 (grease supply portion) that supplies grease to the meshing portion 34 when the worm wheel 32 rotates in a first direction (clockwise as indicated by arrow (1)), and a second grease supply portion 52 that supplies grease to the meshing portion 34 when the worm wheel 32 rotates in a second direction (counterclockwise as indicated by arrow (2)) opposite to the first direction. The first grease supply portion 51 is located on the right side (one side) of the first reference plane P1, and the second grease supply portion 52 is located on the left side (the other side) of the first reference plane P1.

[0034] (Supporting Portion) Please refer to Figures 4 and 5. The first grease supplying portion 51 has a supporting portion 70 which supports an end portion 61 of a grease receiving portion 60 (described later) and is formed integrally with the grease receiving portion 60.

[0035] The support part 70 is overlapped and fixed to the inner surface 42a of the lid 42. The fixing method may be selected appropriately from well-known techniques such as adhesive, screw fastening, or crimping. The member that overlaps and fixes the support part 70 is not limited to the lid 42, but may also be the box 41. The grease receiving part 60 is separated from the lid 42 and is supported only by the support part 70.

[0036] 3A and 3B, when viewed from the direction along the rotation axis Ax, the end 61 of the grease receiving portion 60 extends in, for example, substantially the same direction as the rotation axis Ax of the worm gear 31.

[0037] Of the two ends 61a, 61b of the end 61 of the grease receiving portion 60, the end closer to the rotation axis Ax is the inner end 61a, and the end farther from the rotation axis Ax is the outer end 61b.

[0038] (Weakened portion) The end 61 of the grease receiving portion 60 is set as a weakened portion 51A that is weaker than the surrounding portions of the grease receiving portion 60. For example, the weakened portion 51A may be set by setting the thickness of the plate material thinner than the surrounding portions, or by forming a lightening hole. The weakened portion 51A may be set as appropriate within the first grease supply portion 51.

[0039] (Shape of Support Portion 70) See Fig. 3B. The support portion 70 is generally band-shaped and is configured by connecting an arc portion 71 having an arc shape centered on the rotation axis Ax and a linear portion 72 extending from an end of the arc portion 71 toward the worm gear 31.

[0040] The configuration of the support portion 70 is not important as long as the support portion 70 has an overlapping surface 70a that overlaps the inner surface 42a of the lid 42. The support portion 70 overlaps the second reference plane P2. The grease receiving portion 60 is located closer to the worm gear 31 than the second reference plane P2.

[0041] 4 and 5 . The grease receiving portion 60 has a guide end point portion 60a that is closest to the meshing portion 34, and an end face adjacent portion 62 that has the guide end point portion 60a at one end and is provided linearly along the end face 33 of the worm wheel 32. A gap may be provided between the end face adjacent portion 62 and the end face 33, or the end face adjacent portion 62 may be in contact with the end face 33.

[0042] The end of the end face adjacent portion 62 opposite the guide end point portion 60a is referred to as an opposite end portion 62a. See Fig. 3A. The opposite end portion 62a is located on the inner peripheral edge 33b of the annular end face 33. That is, the length of the end face adjacent portion 62 is set to correspond to the entire width of the end face 33 of the worm wheel 32.

[0043] When viewed from a direction along the rotation axis Ax (see FIG. 3A ), the end face proximity portion 62 is inclined with respect to the first reference plane P1 (inclination angle θ1). Note that the end face proximity portion 62 may overlap the first reference plane P1 (inclination angle θ1=0°).

[0044] (Grease Receptacle Main Body) See Figures 4 and 5. The grease receiver 60 has a grease receiver main body 63 that includes a guide end point 60a and is arranged so as to stand upright relative to the end face 33. The grease receiver main body 63 is capable of directly receiving grease adhering to the end face 33. This grease receiver main body 63 does not necessarily stand perpendicular to the end face 33, but may be at an angle as described below. Furthermore, the grease receiver main body 63 has the following two portions whose normal directions are different from each other.

[0045] (Lower Grease Receptacle) The grease receptacle body 63 has a lower grease receptacle 64 having a triangular plane with both ends 60a, 62a of the end face adjacent portion 62 and the inner end 61a of the end 61 of the grease receptacle 60 as its vertex.

[0046] 6B , the grease receiver lower portion 64 is inclined inward (toward the first reference plane P1) with respect to the perpendicular direction of the end face 33 of the worm wheel 32 (see inclination angle θ2). Note that the grease receiver lower portion 64 may be inclined outward (away from the first reference plane P1) with respect to the perpendicular direction of the end face 33, or may be perpendicular to the end face 33.

[0047] (Upper Grease Receptacle) See Figure 4. Above the lower grease receiver 64 is located the upper grease receiver 65 (inclined portion) having a triangular plane including the guide end point 60a and the inner end 61a. See Figure 5. The apex 66a of the triangle formed by the guide end point 60a and the inner end 61a is located above the guide end point 60a.

[0048] See Figure 6A. The grease receiver upper part 65 is inclined in a direction away from the first reference plane P1 (see inclination angle θ3) with respect to the perpendicular direction of the end face 33 of the worm wheel 32. The grease receiver upper part 65 may also be perpendicular to the end face 33. The linear portion connecting the apex 66a and the guide end point 60a is defined as the upper tip part 66. The upper tip part 66, together with an upper tip part 86 (described later), forms a V shape (when viewed in the direction from the meshing part 34 toward the rotation axis Ax).

[0049] With the above-described configuration (see the inclination angles θ2 and θ3), the cross section of the grease receiver body 63 is bent so as to protrude in a direction approaching the first reference plane P1. The grease receiver upper part 65 and the grease receiver lower part 64 may be located on the same plane.

[0050] (Grease Receiving Auxiliary Portion) See Figures 4 and 5. A grease receiving auxiliary portion 67 is located above the grease receiving upper portion 65 and has a flat surface that does not include the guide end point portion 60a and faces the end face 33. The grease receiving auxiliary portion 67 can indirectly receive grease adhering to the end face 33. In other words, it is positioned to further receive the grease received by the grease receiving main body portion 63.

[0051] The grease receiving auxiliary portion 67 has a plane including the vertex 66a, the inner end portion 61a, and the outer end portion 61b. See FIG. 3B. The grease receiving auxiliary portion 67 has a substantially parallelogram shape when viewed from a direction along the rotation axis Ax. The grease receiving auxiliary portion 67 is a portion extending from the end portion 61 of the grease receiving portion 60, and is inclined so as to approach the first reference plane P1 as it approaches the meshing portion 34. See FIG. 5. The grease receiving auxiliary portion 67 is inclined so as to approach the end face 33 as it approaches the meshing portion 34.

[0052] 4 and 5, the grease receiving portion 60 has a receiving portion rib 68 formed across the entire grease receiving lower portion 64, the grease receiving upper portion 65, and the grease receiving auxiliary portion 67. The receiving portion rib 68 is substantially perpendicular to the end face 33 of the worm wheel 32 and extends in a direction perpendicular to the first reference plane P1.

[0053] The receiving portion rib 68 includes the opposite end portion 62 a of the end face proximity portion 62. Therefore, the receiving portion rib 68 can prevent the grease received by the grease receiving portion 60 from moving in a direction away from the meshing portion 34.

[0054] (Second grease supply portion 52) See FIG. 3B. The second grease supply portion 52 has a symmetrical shape to the first grease supply portion 51 with respect to the first reference plane P1. The second grease supply portion 52 includes a support portion 90 and a grease receiving portion 80. The support portion 70 has an arc portion 91 and a linear portion 92. The grease receiving portion 80 includes an end portion 81 of the grease receiving portion 50, a grease receiving main body portion 83, a grease receiving auxiliary portion 87, an end face adjacent portion 82, an opposite end portion 82a, and an upper tip portion 86.

[0055] The description of the above components and other components can be appropriately interpreted as replacing the description of the components of the first grease supply unit 51. A detailed description of the components of the second grease supply unit 52 will be omitted.

[0056] An end 70b of the support portion 70 of the first grease supply portion 51 (the end opposite to the portion supporting the end 61 of the grease receiving portion 60) and an end 90b of the support portion 90 of the second grease supply portion 52 (the end opposite to the portion supporting the end 81 of the grease receiving portion 80) overlap the first reference plane P1. In other words, the support portion 70 and the support portion 90 are formed contiguously.

[0057] 3B and 4 . The end face adjacent portion 62 of the first grease supply portion 51 and the end face adjacent portion 82 of the second grease supply portion 52 are integrated via the connection portion 53. The connection portion 53 is a triangular member whose vertices are the guide end point portion 60 a, the opposite end portion 62 a of the end face adjacent portion 62, and the opposite end portion 82 a of the end face adjacent portion 82. When viewed from a direction along the rotation axis Ax, the grease receiving portion 60 and the grease receiving portion 80 are V-shaped.

[0058] 6B , the connecting portion 53 has an opposing surface 53 a that faces the end surface 33 of the worm wheel 32. A gap may be provided between the opposing surface 53 a and the end surface 33, or the opposing surface 53 a may be in contact with the end surface 33.

[0059] (First Effect) See Figure 7. When the worm gear mechanism 30 operates, highly viscous grease G inevitably adheres to the end face 33 of the worm wheel 32. The worm gear mechanism 30 includes a first grease supply unit 51 that can supply the grease G adhered to the end face 33 of the worm wheel 32 to the meshing portion 34. When the worm wheel 32 rotates clockwise, the grease G adhered to the end face 33 of the worm wheel 32 also moves in the rotational direction, as shown by arrow (3).

[0060] The first grease supplying portion 51 has a grease receiving portion 60 provided at a position where it can come into contact with and receive the grease G that moves together with the end face 33 .

[0061] 4 and 5, the grease receiving portion 60 has a grease receiving main body portion 63 that is disposed so as to stand upright relative to the end surface 33. The grease that moves toward the grease receiving main body portion 63 comes into contact with the grease receiving main body portion 63, and the grease collects in the grease receiving main body portion 63.

[0062] Since the grease receiver main body 63 includes the guide end point 60a, as shown by the arrow (4) in Figure 7, the grease collected in the grease receiver main body 63 is supplied toward the meshing portion 34. Therefore, it is possible to provide a worm gear mechanism 30 that can maintain a lubricated state with the grease G.

[0063] 4 and 5, the first grease supply unit 51 is configured by integrating a grease receiving unit 60 and a support unit 70. The support unit 70 is superimposed on and fixed to the inner surface 42a of the lid 42 of the housing 40, and the support unit 70 itself is firmly fixed to the lid 42.

[0064] On the other hand, the end 61 of the grease receiving portion 60 is supported by the support portion 70 and is spaced apart from the lid 42. In the event of excessive thermal deformation or an external load being input to the lid 42, causing the first grease supply portion 51 to come into contact with the worm wheel 31, a load will be applied to the first grease supply portion 51. When such a load is applied to the first grease supply portion 51, the load will be concentrated at the end 61 of the grease receiving portion 60. The first grease supply portion 51 will easily separate into the support portion 70 and the grease receiving portion 60, with the end 61 of the grease receiving portion 60 as the boundary. The first grease supply portion 51 will not be broken into small pieces, and will be prevented from being absorbed into the worm gear 31.

[0065] (Third Effect) See Fig. 2. By fixing the support part 70 to the inner surface 42a of the lid 42, the work of fixing the first grease supply part 51 is easier than when fixing it to the box 41, for example.

[0066] 3A and 5. When viewed from the direction along the rotation axis Ax, the end face adjacent portion 62 is disposed at an angle with respect to the first reference plane P1 (inclination angle θ1). Grease that moves with the rotation of the end face 33 of the worm wheel 32 strikes the grease receiver main body portion 63 at an angle, which makes it easier for the grease to move toward the meshing portion 34. The end face adjacent portion 62 may also be disposed so as to overlap the first reference plane P1.

[0067] 6A , the upper grease receiving portion 65 (inclined portion) is inclined (at an inclination angle θ3) in a direction away from the first reference plane P1, with the perpendicular direction of the end face 33 of the worm gear 31 as a reference. This can prevent grease from scattering when the grease receiving portion 60 receives grease.

[0068] (Sixth Effect) See Figure 4. The first grease supply portion 51 has a weak portion 51A that is weaker than the surrounding portions of the grease receiving portion 60. By setting the weak portion 51A in advance, when a load is applied to the first grease supply portion 51, the grease receiving portion 60 is more likely to separate into two portions at the weak portion 51A. This makes it possible to prevent the separated portions from becoming caught between the worm wheel 32 and the worm gear 31.

[0069] (Seventh Effect) The fragile portion 51A is provided at the end 61 of the grease receiving portion 60. Therefore, the first grease receiving portion 60 can be easily separated into the grease receiving portion 60 and the support portion 70. This can prevent the grease receiving portion 60 from being caught between the worm wheel 32 and the worm gear 31.

[0070] (Eighth Advantage) See Fig. 7. The grease supplier 50 includes a second grease supplier 52 in addition to a first grease supplier 51. The second grease supplier 52 includes a second grease receiver 60.

[0071] When the worm wheel 32 rotates counterclockwise (see arrow (2)), the second grease supply portion 52 can supply the grease adhering to the end face 33 of the worm wheel 32 to the meshing portion 34.

[0072] If the worm gear mechanism is one in which the worm wheel 32 rotates only in either a clockwise or counterclockwise direction, only one of the first grease supply portion 51 or the second grease supply portion 52 is required, depending on the direction of rotation.

[0073] In the worm gear mechanism 30 of the electric power steering device 10, the worm wheel 32 rotates both clockwise and counterclockwise. In such a case, by using the grease supplier 50 that includes both the first grease supplier 51 and the second grease supplier 52, grease can be supplied toward the meshing portion 34 regardless of the rotation direction of the worm wheel 32.

[0074] (Ninth Effect) The second grease supply portion 52 has a symmetrical shape to the first grease supply portion 51 with respect to the first reference plane P1. Therefore, grease can be uniformly supplied to the meshing portion 34 regardless of the rotation direction of the worm wheel 32. Note that the shape of the second grease supply portion 52 may be asymmetrical to the shape of the first grease supply portion 51.

[0075] (Tenth Effect) The end 70b of the support portion 70 of the first grease supply portion 51 and the end 90b of the fixing portion 90 of the second grease supply portion 52 are formed to be continuous. Furthermore, the end face adjacent portion 62 of the second grease supply portion 52 is formed to be continuous with the end face adjacent portion 62 of the first grease supply portion 51 via the connecting portion 53. In other words, the first grease supply portion 51 and the second grease supply portion 52 are integrated to form the grease supply body 50. The strength of the grease supply body 50 is increased. This grease supply body 50 is annular and surrounds the rotation axis Ax.

[0076] (Eleventh Effect) The electric power steering device 10 includes a worm gear 31 that rotates by the driving force generated by the electric motor 33, a worm wheel 32 that meshes with the worm gear 31 and transmits the driving force of the electric motor 33 to the steering rack, and a grease supply unit 50 that can supply grease adhering to the end face 33 of the worm wheel 32 to the meshing portion 34 when the meshing portion 34 is the portion where the worm wheel 32 and the worm gear 31 mesh most deeply with each other when viewing the end face 33 of the worm wheel 32 from a direction along the rotation axis Ax of the worm wheel 32.

[0077] The grease supply unit 50 is provided at a position where it can come into contact with and receive grease adhering to the end face 33 of the worm wheel 32 as the worm wheel 32 rotates, and has a grease receiving portion 60 that supplies the received grease toward the meshing portion 34. Therefore, it is possible to provide an electric power steering device 10 equipped with a worm gear mechanism 30 that can maintain a lubricated state with grease. The worm gear 30 used in the electric power steering device 10 is placed in a severe thermal environment, and therefore there is a particularly high need to maintain a lubricated state with grease.

[0078] As long as the functions and effects of the present invention are achieved, the present invention is not limited to the examples. In particular, the configuration of the grease receiving portion 60, which is provided from the end face adjacent portion 62 to the end portion 61, can be modified as appropriate as long as it is arranged to stand against the end face 33 of the worm wheel 32 to receive grease and can supply grease toward the meshing portion 34. The terms up, down, left, and right are used for convenience in describing the worm gear mechanism 30 and do not limit the orientation of the worm gear mechanism 30 when it is in operation. The worm gear mechanism 30 is not limited to the one provided in the electric power steering 10, and the drive source of the worm gear 31 can also be selected as appropriate.

[0079] DESCRIPTION OF SYMBOLS 10... Electric power steering device 14... Electric motor 30... Worm gear mechanism 31... Worm gear 32... Worm wheel, 32a... Shaft portion 33... End surface of worm wheel, 33a... Outer peripheral edge, 33b... Inner peripheral edge 34... Meshing portion 40... Housing 41... Box, 41a... Opening 42... Lid 50... Grease supply body 51... First grease supply portion (grease supply portion) 52... Second grease supply portion 60... Grease receiving portion 60a... Guide end point portion 61... End portion of grease receiving portion 62... End face adjacent portion 63... Grease receiving main body portion 65... Upper portion of grease receiving (inclined portion) Ax... Rotation axis of worm wheel P1... First reference plane (reference plane)

Claims

1. a worm gear that rotates by a driving force generated by a driving source; a worm wheel that meshes with the worm gear; a housing that accommodates the worm gear and the worm wheel; a grease supply unit capable of supplying grease adhering to the end surface of the worm wheel to the meshing portion, the meshing portion being defined as a portion where the worm wheel and the worm gear mesh most deeply with each other when the end surface of the worm wheel is viewed from a direction along the rotation axis of the worm wheel; The grease supply unit is a grease receiving portion that is provided at a position where the grease receiving portion can come into contact with and receive grease adhering to an end surface of the worm wheel when the worm wheel rotates, and that supplies the received grease toward the meshing portion; a support portion that supports an end portion of the grease receiving portion, is formed integrally with the grease receiving portion, and is superimposed on and fixed to the housing, A worm gear mechanism, wherein an end of the grease receiving portion is set as a weak portion that is weaker than surrounding portions of the grease supply portion.

2. The housing includes a box having an opening and a lid that closes the opening. The worm gear mechanism according to claim 1 , wherein the support is fixed to the lid.

3. the grease receiving portion has a guide end point portion closest to the meshing portion, and an end face adjacent portion provided linearly from the guide end point portion along the end face of the worm wheel, a plane including the rotation axis of the worm wheel and the meshing portion is defined as a reference plane; 2. The worm gear mechanism according to claim 1, wherein the end face adjacent portion is disposed at an angle with respect to the reference plane when viewed from a direction along the rotation axis of the worm wheel.

4. the grease receiving portion includes a guide end point portion closest to the meshing portion and a grease receiving main body portion arranged to stand upright against an end face of the worm wheel, a plane including the rotation axis of the worm wheel and the meshing portion is defined as a reference plane; 2. The worm gear mechanism according to claim 1, wherein the grease receiving body includes an inclined portion that is inclined in a direction away from a reference plane that is perpendicular to the end face of the worm wheel.

5. a second grease supply unit that is provided at a position where it can come into contact with grease adhering to the end face of the worm wheel when the worm wheel rotates and receive the grease, and that supplies the received grease toward the meshing portion; a plane including the rotation axis of the worm wheel and the meshing portion is defined as a reference plane; the grease supplying portion is located on one side of the reference surface as a boundary, 2. The worm gear mechanism according to claim 1, wherein the second grease supply portion is located on the other side of the reference surface.

6. 6. The worm gear mechanism according to claim 5, wherein the second grease supply portion has a shape symmetrical to the first grease supply portion with respect to the reference plane.

7. 7. The worm gear mechanism according to claim 6, wherein the grease supply portion and the second grease supply portion are integrated and have an annular shape surrounding the rotation axis when viewed from a direction along the rotation axis of the worm wheel.

8. a worm gear that rotates by a driving force generated by an electric motor; a worm wheel that meshes with the worm gear and transmits the driving force of the electric motor to a steering rack; a housing that accommodates the worm gear and the worm wheel; a grease supply unit capable of supplying grease adhering to the end surface of the worm wheel to the meshing portion, the meshing portion being defined as a portion where the worm wheel and the worm gear mesh most deeply with each other when the end surface of the worm wheel is viewed from a direction along the rotation axis of the worm wheel; The grease supply unit is a grease receiving portion that is provided at a position where the grease receiving portion can come into contact with and receive grease adhering to an end surface of the worm wheel when the worm wheel rotates, and that supplies the received grease toward the meshing portion; a support portion that supports an end portion of the grease receiving portion, is formed integrally with the grease receiving portion, and is superimposed on and fixed to the housing; An electric power steering device, wherein an end of the grease receiving portion is set as a weak portion that is weaker than surrounding portions of the grease supply portion.