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

Abstract

The worm gear mechanism (30) is provided with a grease supply unit (51) capable of supplying grease adhering to the end surface (33) of the worm gear (32) to the meshing part (34). The grease supply unit (51) is provided with a grease receiving unit (60) that is provided at a position at which grease adhering to the end surface (33) of the worm wheel (32) can be brought into contact during rotation of the worm wheel (32), thereby receiving the grease, and that supplies the received grease toward the meshing unit (34).

Description

Technical Field

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

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

[0003] Since slip occurs on the meshing surfaces of the worms, it is important to maintain the lubrication of the meshing surfaces by applying grease to the meshing surfaces. Patent Document 1 discloses an example of conventional technology for maintaining lubrication of the meshing surfaces.

[0004] A grease retaining plate with a larger diameter than the worm wheel's outer diameter is attached to the lower end face of the worm wheel disclosed in Patent Document 1. The outer periphery of the grease retaining plate is bent upward to prevent grease from flowing radially outward. Furthermore, multiple ribs are formed along the circumference of the plate to mesh with the worm wheel. This structure retains grease on the meshing surface, maintaining lubrication.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-248724 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, when a worm gear mechanism operates, some of the grease applied to the meshing surfaces inevitably flows out toward the end face of the worm gear. Grease is also highly viscous among lubricants. Grease that flows out of the meshing surfaces remains attached to the end face of the worm gear, thus requiring improvement.

[0010] An object of the present invention is to provide a worm gear mechanism capable of maintaining a lubricated state of grease, and an electric power steering including the worm gear mechanism.

[0011] Means for solving problems

[0012] First, a worm gear mechanism is provided, which comprises:

[0013] a worm that is rotated by a driving force generated by a driving source;

[0014] a worm wheel meshing with the worm; and

[0015] a grease supply portion configured to supply grease adhering to the end face of the worm wheel to the meshing portion where the worm wheel and the worm are most deeply meshed with each other when the end face of the worm wheel is viewed from a direction along the rotation axis of the worm wheel,

[0016] The grease supply portion has a grease receiving portion, which is arranged at a position where it can contact the grease attached to the end surface of the worm wheel when the worm wheel rotates and receive the grease. The grease receiving portion supplies the received grease to the meshing portion.

[0017] Second, preferably, in the worm gear mechanism described first,

[0018] The worm gear mechanism includes a housing for accommodating the worm and the worm wheel.

[0019] The grease supply portion includes a support portion that supports the end portion of the grease receiving portion and is formed integrally with the grease receiving portion.

[0020] The support portion is fixed to the housing so as to overlap with the housing.

[0021] Third, preferably, in the worm gear mechanism described in the second embodiment,

[0022] The housing includes a box having an opening and a cover for closing the opening.

[0023] The support portion is fixed to the cover.

[0024] Fourth, preferably, in the worm gear mechanism described first,

[0025] The grease receiving portion includes a guide end portion closest to the meshing portion and an end face approaching portion linearly arranged from the guide end portion along the end face of the worm wheel.

[0026] Assuming that the plane including the rotation axis of the worm wheel and the meshing portion is a reference plane,

[0027] The end surface approach portion is arranged to be inclined with respect to the reference plane when viewed from a direction along the rotation axis of the worm wheel.

[0028] Fifth, preferably, in the worm gear mechanism described first,

[0029] The grease receiving portion includes a grease receiving body portion, the grease receiving body portion including a guide end portion closest to the meshing portion and arranged in a manner standing relative to the end surface of the worm wheel.

[0030] Assuming that the plane including the rotation axis of the worm wheel and the meshing portion is a reference plane,

[0031] The grease receiving body includes an inclined portion, and the inclined portion is arranged to be inclined in a direction away from a reference plane with respect to a vertical direction of the end surface of the worm wheel.

[0032] Sixth, preferably, in the worm gear mechanism according to any one of the first to fifth aspects,

[0033] The grease supply portion includes a fragile portion that is fragile than surrounding portions of the grease supply portion.

[0034] Seventh, preferably, in the worm gear mechanism described in the sixth aspect,

[0035] The fragile portion is provided at an end portion of the grease receiving portion or the grease receiving portion.

[0036] Eighth, preferably, in the worm gear mechanism described first,

[0037] The worm gear mechanism includes a second grease supply portion, which is provided at a position where it can contact the grease adhered to the end surface of the worm gear when the worm gear rotates and receive the grease, and the second grease supply portion supplies the received grease to the meshing portion.

[0038] Assuming that the plane including the rotation axis of the worm wheel and the meshing portion is a reference plane,

[0039] The grease supply portion is located on one side with the reference surface as a boundary.

[0040] The second grease supply portion is located on the other side with the reference surface as a boundary.

[0041] Ninth, preferably, in the worm gear mechanism described in eighth,

[0042] The second grease supply portion has a symmetrical shape with respect to the reference plane.

[0043] Tenth, preferably, in the worm gear mechanism described in the ninth,

[0044] The grease supply portion and the second grease supply portion are integrated, and when viewed from a direction along the rotation axis of the worm wheel, the grease supply portion and the second grease supply portion are annular so as to surround the rotation axis.

[0045] Eleventh, an electric power steering device is provided, comprising:

[0046] a worm gear that is rotated by a driving force generated by an electric motor;

[0047] a worm gear meshing with the worm gear to transmit the driving force of the electric motor to the steering rack; and

[0048] a grease supply portion configured to supply grease adhering to the end face of the worm wheel to the meshing portion where the worm wheel and the worm are most deeply meshed with each other when the end face of the worm wheel is viewed from a direction along the rotation axis of the worm wheel,

[0049] The grease supply portion has a grease receiving portion, which is arranged at a position where it can contact the grease attached to the end surface of the worm wheel when the worm wheel rotates and receive the grease. The grease receiving portion supplies the received grease to the meshing portion.

[0050] Effects of the Invention

[0051] The present invention provides a worm gear mechanism capable of maintaining a lubricated state of grease, and an electric power steering including the worm gear mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of an electric power steering system equipped with a worm gear mechanism.

[0053] Figure 2 It is an exploded perspective view of the worm gear mechanism.

[0054] Figure 3A It is a diagram illustrating the worm wheel and the worm as viewed from a direction along the rotation axis of the worm wheel. Figure 3B It is a diagram illustrating the grease supply body (grease supply portion) viewed from a direction along the rotation axis of the worm wheel.

[0055] Figure 4 This is a perspective view of the grease supply unit as seen from below.

[0056] Figure 5 It is a diagram illustrating a grease supply portion and a worm gear mechanism viewed from the side.

[0057] Figure 6A This is a diagram illustrating the grease supply portion as viewed from the meshing portion toward the rotation axis of the worm wheel. Figure 6B It is a diagram illustrating a cross section of a grease receiving portion.

[0058] Figure 7 This is a diagram for explaining the function of the grease supply body (grease supply portion). DETAILED DESCRIPTION

[0059] <Example>

[0060] The embodiment will be described with reference to the accompanying drawings. In addition, L represents left, R represents right, Up represents up, and Dn represents down.

[0061] Reference Figure 1 The electric power steering device 10 includes a steering mechanism 20 extending from a steering wheel 21 of the vehicle to steered wheels 29 , 29 (for example, front wheels) of the vehicle, and an assist torque mechanism 11 for applying assist torque to the steering mechanism 20 .

[0062] In the steering mechanism 20, the pinion shaft 24 is connected to the steering wheel 21 via the steering shaft 22 and the universal joints 23, 23, the rack shaft 26 (steering rack) is connected to the pinion shaft 24 via the rack and pinion mechanism 25, and the left and right steered wheels 29, 29 are connected at both ends of the rack shaft 26 via the left and right tie rods 27, 27 and the steering knuckles 28, 28.

[0063] The rack and pinion mechanism 25 is composed of a pinion 24 a formed on the pinion shaft 24 and a rack 26 a formed on the rack shaft 26 .

[0064] According to the above configuration, when the driver steers the steering wheel 21 , the left and right steered wheels 29 , 29 can be steered using the steering torque via the rack and pinion mechanism 25 and the left and right tie rods 27 , 27 .

[0065] The assist torque mechanism 11 detects the steering torque of the steering mechanism 20 applied to the steering wheel 21 using a steering torque sensor 12. Based on the torque detection signal from the steering torque sensor 12, the control unit 13 generates a control signal. Based on this control signal, the electric motor 14 (drive source) generates an assist torque corresponding to the steering torque. This assist torque is then transmitted to the rack shaft 26 via the worm gear mechanism 30. Alternatively, the assist torque of the worm gear mechanism 30 may be transmitted to the pinion shaft 24.

[0066] (Worm gear mechanism)

[0067] Reference Figure 2 The worm gear mechanism 30 includes a worm 31 which is driven by an electric motor 33 (see Figure 1 ) is rotated by the driving force generated by the worm wheel 32; a worm wheel 32 meshing with the worm 31; and a housing 40 that accommodates the worm 31 and the worm wheel 32.

[0068] (housing, axis of rotation)

[0069] The housing 40 includes a box 41 having an opening 41a opened upward and a cover 42 that closes the opening 41a of the box 41. The cover 42 is fixed to the box 41 by fastening members 43, 43 such as bolts. The shaft 32a of the worm wheel 32 is connected to the rack shaft 26 (see FIG. Figure 1The rotation axis Ax of the shaft portion 32a extends in a direction passing through the cover 42.

[0070] (Meshing part)

[0071] Reference Figure 3A When the annular end surface 33 of the worm wheel 32 is viewed from the direction along the rotation axis Ax of the worm wheel 32 , the portion where the outer peripheral edge 33 a of the end surface 33 of the worm wheel 32 and the worm 31 mesh most deeply with each other is defined as the meshing portion 34 .

[0072] (Grease supply body)

[0073] Reference Figures 2 to 3B The worm gear mechanism 30 further includes a grease supply body 50 capable of supplying grease adhering to the end surface 33 of the worm wheel 32 to the meshing portion 34 . The grease supply body 50 is disposed between the cover 42 and the end surface 33 of the worm wheel 32 .

[0074] The grease supply body 50 is made of resin. The resin comprising the grease supply body 50 contains long fibers, such as glass fibers or carbon fibers. The material comprising the grease supply body 50 is not limited to metal, as long as it has the required rigidity. All components of the grease supply body 50 are plate-shaped.

[0075] (First reference plane, second reference plane)

[0076] A plane including the rotation axis Ax of the worm wheel 32 and the meshing portion 34 is referred to as a first reference plane P1. A plane including the rotation axis Ax and perpendicular to the first reference plane P1 is referred to as a second reference plane P2.

[0077] (First grease supply unit, second grease supply unit)

[0078] 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 direction 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 direction 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.

[0079] (Supporting part)

[0080] Reference Figure 4 and Figure 5 The first grease supply portion 51 includes a support portion 70 that supports an end portion 61 of a grease receiving portion 60 described later and is formed integrally with the grease receiving portion 60 .

[0081] The support portion 70 is fixedly attached to the inner surface 42a of the cover 42. The fixing method may be appropriately selected from known techniques such as adhesives, screw fastening, and riveting. The member to which the support portion 70 is attached is not limited to the cover 42; the case 41 may also be used. The grease receiving portion 60 is separate from the cover 42 and is supported only by the support portion 70.

[0082] (End of grease receiving portion)

[0083] Reference Figure 3A and Figure 3B When viewed from the direction along the rotation axis Ax, the end portion 61 of the grease receiving portion 60 extends in, for example, a direction substantially the same as the direction in which the rotation axis Ax of the worm 31 extends.

[0084] Of the two ends 61 a and 61 b ​​of the end portion 61 of the grease receiving portion 60 , the end portion closer to the rotation axis Ax is referred to as the inner end portion 61 a , and the end portion farther from the rotation axis Ax is referred to as the outer end portion 61 b ​​.

[0085] (Vulnerable Ministry)

[0086] The end 61 of the grease receiving portion 60 is formed as a fragile portion 51A, which is weaker than the surrounding portion of the grease receiving portion 60. The fragile portion 51A can be formed by, for example, making the plate thinner than the surrounding portion or forming a hollow hole. The fragile portion 51A can be appropriately provided in the first grease supply portion 51.

[0087] (Shape of Supporting Portion 70)

[0088] Reference Figure 3B The support portion 70 is generally strip-shaped and is composed of an arc portion 71 centered on the rotation axis Ax and a linear portion 72 extending from the end of the arc portion 71 toward the worm 31 .

[0089] The support portion 70 has no particular limitations on its structure as long as it has an overlapping surface 70a that overlaps the inner surface 42a of the cover 42. The support portion 70 overlaps the second reference plane P2. The grease receiving portion 60 is located closer to the worm 31 than the second reference plane P2.

[0090] (Guide end point, end surface 33 approach portion)

[0091] Reference Figure 4 and Figure 5The grease receiving portion 60 includes a guide terminal portion 60a closest to the meshing portion 34 and an end surface approach portion 62 extending linearly along the end surface 33 of the worm wheel 32, with the guide terminal portion 60a at one end. A gap may be provided between the end surface approach portion 62 and the end surface 33, or the end surface approach portion 62 may be in contact with the end surface 33.

[0092] The end portion of the end surface approach portion 62 on the opposite side to the guide terminal end portion 60a is referred to as the opposite side end portion 62a. Figure 3A The opposite end portion 62 a is located at the inner peripheral edge 33 b of the annular end surface 33 . That is, the length of the end surface approach portion 62 is set to correspond to the entire width direction of the end surface 33 of the worm wheel 32 .

[0093] When viewed from the direction along the rotation axis Ax (see Figure 3A ), the end surface approach portion 62 is inclined relative to the first reference plane P1 (inclination angle θ1). Alternatively, the end surface approach portion 62 may overlap with the first reference plane P1 (inclination angle θ1 = 0°).

[0094] (Grease receiving body)

[0095] Reference Figure 4 and Figure 5 The grease receiving portion 60 includes a grease receiving body portion 63, which includes a guide end portion 60a and is arranged to stand upright relative to the end face 33. The grease receiving body portion 63 can directly receive grease attached to the end face 33. The grease receiving body portion 63 is not limited to standing upright relative to the end face 33, and can also be inclined as described below. In addition, the grease receiving body portion 63 has the following two parts whose normal directions are different from each other.

[0096] (Grease receiving lower part)

[0097] The grease receiving body 63 has a grease receiving lower portion 64 having a triangular plane with the two ends 60a, 62a of the end surface approach portion 62 and the inner end 61a of the end portion 61 of the grease receiving portion 60 as vertices.

[0098] Reference Figure 6B The grease receiving lower portion 64 is inclined inward (toward the first reference plane P1) relative to the direction perpendicular to the end surface 33 of the worm wheel 32 (see inclination angle θ2). Alternatively, the grease receiving lower portion 64 may be inclined outward (away from the first reference plane P1) relative to the direction perpendicular to the end surface 33 or may be perpendicular to the end surface 33.

[0099] (Grease receiving upper part)

[0100] Reference Figure 4The grease receiving upper portion 65 (inclined portion) has a triangular plane including the guide end portion 60a and the inner end portion 61a, and the grease receiving upper portion 65 (inclined portion) is located above the grease receiving lower portion 64. Figure 5 The vertex 66a that forms a triangle together with the guide end point 60a and the inner end 61a is located above the guide end point 60a.

[0101] Reference Figure 6A . The upper portion 65 of the grease receiving portion is inclined in a direction away from the first reference plane P1 with respect to the vertical direction of the end face 33 of the worm wheel 32 (see the inclination angle θ3). In addition, the upper grease receiving portion 65 can also be perpendicular to the end face 33. The straight portion connecting the vertex 66a and the guide end portion 60a is referred to as the upper terminal portion 66. The upper terminal portion 66 forms a V-shape together with the upper terminal portion 86 described later (when viewed from the direction of the meshing 34 toward the rotation axis Ax).

[0102] With the above structure (see inclination angles θ2 and θ3), the cross section of the grease receiving body 63 is bent so as to protrude toward the first reference plane P1. Alternatively, the grease receiving upper portion 65 and the grease receiving lower portion 64 may be located on the same plane.

[0103] (Grease receiving auxiliary part)

[0104] Reference Figure 4 and Figure 5 The auxiliary grease receiving portion 67 has a flat surface facing the end face 33, excluding the guide end point 60a. The auxiliary grease receiving portion 67 is located above the upper grease receiving portion 65. The auxiliary grease receiving portion 67 can indirectly receive grease adhering to the end face 33. In other words, it is configured to further receive grease received by the main grease receiving portion 63.

[0105] The grease receiving auxiliary portion 67 has a plane including the apex 66a, the inner end portion 61a, and the outer end portion 61b. Figure 3B The auxiliary grease receiving portion 67 is substantially parallelogram-shaped when viewed from the direction along the rotation axis Ax. The auxiliary grease receiving 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. Figure 5 The auxiliary grease receiving portion 67 is inclined so as to approach the end surface 33 as it approaches the meshing portion 34 .

[0106] (Connecting rib)

[0107] Reference Figure 4 and Figure 5The grease receiving portion 60 has a receiving portion rib 68 formed throughout 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 surface 33 of the worm wheel 32 and extends in a direction perpendicular to the first reference plane P1.

[0108] The receiving portion rib 68 includes an end portion 62a on the opposite side of the end surface proximity portion 62. Therefore, the receiving portion rib 68 can suppress the grease received by the grease receiving portion 60 from moving in a direction away from the meshing portion 34.

[0109] (Second grease supply portion 52)

[0110] Reference Figure 3B The second grease supply portion 52 is symmetrical with the first grease supply portion 51 relative 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 includes an arc portion 91 and a straight 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 approach portion 82, an opposite end portion 82a, and an upper terminal portion 86.

[0111] The description of the above-mentioned components and other components can be appropriately replaced with the description of the components of the first grease supply unit 51. The detailed description of the components of the second grease supply unit 52 will be omitted.

[0112] End 70b of the support portion 70 of the first grease supply portion 51 (the end opposite to the portion supporting end 61 of the grease receiving portion 60) and end 90b of the support portion 90 of the second grease supply portion 52 (the end opposite to the portion supporting end 81 of the grease receiving portion 80) overlap with the first reference plane P1. In other words, the support portion 70 and the support portion 90 are formed so as to be continuous.

[0113] (Connection)

[0114] Reference Figure 3B and Figure 4 The end surface approach portion 62 of the first grease supply portion 51 and the end surface approach portion 82 of the second grease supply portion 52 are integrated via a connecting portion 53. The connecting portion 53 is a triangular member with the guide end point 60a, the opposite end 62a of the end surface approach portion 62, and the opposite end 82a of the end surface approach portion 82 as vertices. When viewed from the direction along the rotation axis Ax, the grease receiving portion 60 and the grease receiving portion 80 form a V-shape.

[0115] Reference Figure 6BThe connecting portion 53 has an opposing surface 53a that opposes the end surface 33 of the worm wheel 32. A gap may be provided between the opposing surface 53a and the end surface 33, or the opposing surface 53a and the end surface 33 may be in contact with each other.

[0116] (First effect)

[0117] Reference Figure 7 When the worm gear mechanism 30 is in operation, the 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 portion 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, as shown by arrow (3), the grease G adhered to the end face 33 of the worm wheel 32 also moves in the direction of rotation.

[0118] The first grease supply portion 51 includes a grease receiving portion 60 provided at a position where the grease receiving portion 60 can come into contact with the grease G that moves together with the end surface 33 and receive the grease.

[0119] Reference Figure 4 and Figure 5 The grease receiving portion 60 includes a grease receiving body portion 63 disposed so as to stand upright relative to the end surface 33 . The moved grease comes into contact with the grease receiving body portion 63 , and the grease is collected in the grease receiving body portion 63 .

[0120] The grease receiving body 63 includes a guide terminal portion 60a, so that Figure 7 As shown by the arrow (4), the grease concentrated in the grease receiving body 63 is supplied to the meshing portion 34. Therefore, the worm gear mechanism 30 capable of maintaining the lubricated state of the grease G can be provided.

[0121] (Second effect)

[0122] Reference Figure 4 and Figure 5 The first grease supply portion 51 is formed by integrating a grease receiving portion 60 and a support portion 70 . The support portion 70 is fixed to the inner surface 42 a of the cover 42 of the housing 40 so as to overlap with the inner surface 42 a. The support portion 70 itself is firmly fixed to the cover 42 .

[0123] Meanwhile, the end 61 of the grease receiving portion 60 is supported by the support portion 70 and is separated from the cover 42. Excessive thermal deformation, external load input to the cover 42, and contact between the first grease supply portion 51 and the worm wheel 31 may exert a load on the first grease supply portion 51. When such a load is applied to the first grease supply portion 51, the load is concentrated on the end 61 of the grease receiving portion 60. The first grease supply portion 51 is easily separated into the support portion 70 and the grease receiving portion 60, with the end 61 of the grease receiving portion 60 serving as the boundary. This prevents the first grease supply portion 51 from being damaged, preventing it from becoming embedded in the worm wheel 31.

[0124] (Third Effect)

[0125] Reference Figure 2 By fixing the support portion 70 to the inner surface 42 a of the cover 42 , the work of fixing the first grease supply portion 51 becomes easier than when fixing the support portion 70 to the case 41 , for example.

[0126] (Fourth Effect)

[0127] Reference Figure 3A and Figure 5 When viewed from the direction along the rotation axis Ax, the end surface approach portion 62 is arranged at an inclination angle (angle θ1) relative to the first reference plane P1. Grease that moves with the rotation of the end surface 33 of the worm wheel 32 contacts the grease receiving body 63 at an inclination angle, thereby facilitating the movement of grease toward the meshing portion 34. Alternatively, the end surface approach portion 62 may be arranged so as to overlap with the first reference plane P1.

[0128] (Fifth Effect)

[0129] Reference Figure 6A The grease receiving upper portion 65 (inclined portion) is inclined (inclined angle θ3) away from the first reference plane P1 relative to the vertical direction of the end surface 33 of the worm 31. This can suppress grease scattering when the grease receiving portion 60 receives grease.

[0130] (Sixth Effect)

[0131] Reference Figure 4 The first grease supply portion 51 includes a fragile portion 51A within the grease receiving portion 60 that is more fragile than the surrounding portion. By pre-setting the fragile portion 51A, the grease receiving portion 60 easily separates into two portions along the fragile portion 51A when a load is applied to the first grease supply portion 51. This prevents the separated portions from becoming engaged between the worm wheel 32 and the worm 31.

[0132] (Seventh Effect)

[0133] 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 prevents the grease receiving portion 60 from being engaged between the worm wheel 32 and the worm 31.

[0134] (Eighth Effect)

[0135] Reference Figure 7 The grease supply body 50 includes a second grease supply portion 52 in addition to the first grease supply portion 51 . The second grease supply portion 52 includes a second grease receiving portion 60 .

[0136] When the worm wheel 32 rotates counterclockwise (see arrow ( 2 )), the second grease supply portion 52 can supply grease adhering to the end surface 33 of the worm wheel 32 to the meshing portion 34 .

[0137] If the worm gear mechanism is one in which the worm wheel 32 rotates only in either clockwise or counterclockwise direction, it is sufficient to have only one of the first grease supply portion 51 and the second grease supply portion 52 depending on the direction of rotation.

[0138] In the worm gear mechanism 30 of the electric power steering device 10, the worm wheel 32 rotates in both the clockwise and counterclockwise directions. In this case, by providing the grease supply body 50 with both the first grease supply portion 51 and the second grease supply portion 52, grease can be supplied to the meshing portion 34 regardless of the rotation direction of the worm wheel 32.

[0139] (Ninth Effect)

[0140] The second grease supply portion 52 is symmetrical with the first grease supply portion 51 relative to the first reference plane P1. Therefore, grease can be uniformly supplied to the meshing portion 34 regardless of the rotational direction of the worm wheel 32. Alternatively, the second grease supply portion 52 may be asymmetrical with the first grease supply portion 51.

[0141] (Tenth Effect)

[0142] The end 70b of the support portion 70 of the first grease supply portion 51 is connected to the end 90b of the fixing portion 90 of the second grease supply portion 52. Furthermore, the end surface proximity portion 62 of the second grease supply portion 52 is connected to the end surface proximity 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. This improves the strength of the grease supply body 50. The grease supply body 50 is annular and surrounds the rotation axis Ax.

[0143] (Eleventh Effect)

[0144] The electric power steering device 10 includes: a worm 31, which is rotated by the driving force generated by the electric motor 33; a worm wheel 32, which meshes with the worm 31 and transmits the driving force of the electric motor 33 to the steering rack; and a grease supply part 50. When the end face 33 of the worm wheel 32 is observed from the direction along the rotation axis Ax of the worm wheel 32, the grease supply part 50 is capable of supplying grease attached to the end face 33 of the worm wheel 32 to the meshing part 34, when the part where the worm wheel 32 and the worm 31 mesh most deeply with each other is assumed to be the meshing part 34.

[0145] The grease supply portion 50 includes a grease receiving portion 60. The grease receiving portion 60 is positioned so as to contact and receive grease adhering to the end surface 33 of the worm wheel 32 when the worm wheel 32 rotates. The grease receiving portion 60 then supplies the received grease to the meshing portion 34. This provides an electric power steering device 10 equipped with a worm gear mechanism 30 capable of maintaining a grease lubricated state. The worm gear 30 used in the electric power steering device 10 is exposed to a harsh thermal environment, making it particularly important to maintain a grease lubricated state.

[0146] Furthermore, the present invention is not limited to the embodiments as long as the functions and effects of the present invention are achieved. In particular, the structure of the grease receiving portion 60, which extends from the end face approach portion 62 to the end portion 61, can be appropriately modified as long as it is configured to stand upright relative to the end face 33 of the worm wheel 32 in order to receive grease and can supply grease toward the meshing portion 34. The terms "up, down, left, and right" are used to facilitate the description of the worm gear mechanism 30 and do not limit the orientation of the worm gear mechanism 30 during operation. The worm gear mechanism 30 is not limited to the mechanism provided by the electric power steering 10, and the drive source of the worm 31 can also be appropriately selected.

[0147] Description of labels

[0148] 10: Electric power steering device;

[0149] 14: Electric motor;

[0150] 30: Worm gear mechanism;

[0151] 31: worm;

[0152] 32: worm gear; 32a: shaft;

[0153] 33: end face of the worm wheel; 33a: outer periphery; 33b: inner periphery;

[0154] 34: meshing portion;

[0155] 40: shell;

[0156] 41: box; 41a: opening;

[0157] 42: cover;

[0158] 50: grease supply body;

[0159] 51: first grease supply portion (grease supply portion);

[0160] 52: second grease supply portion;

[0161] 60: Grease receiving portion;

[0162] 60a: guide terminal portion;

[0163] 61: end of the grease receiving portion;

[0164] 62: end surface approach portion;

[0165] 63: Grease receiving body;

[0166] 65: Grease receiving upper part (inclined part);

[0167] Ax: rotation axis of the worm gear;

[0168] P1: First reference plane (reference plane).

Claims

1. A worm gear mechanism comprising: a worm that is rotated by a driving force generated by a driving source; a worm wheel meshing with the worm; and a grease supply portion configured to supply grease adhering to the end face of the worm wheel to the meshing portion where the worm wheel and the worm are most deeply meshed with each other when the end face of the worm wheel is viewed from a direction along the rotation axis of the worm wheel, The grease supply portion has a grease receiving portion, which is arranged at a position where it can contact the grease attached to the end surface of the worm wheel when the worm wheel rotates and receive the grease. The grease receiving portion supplies the received grease to the meshing portion.

2. The worm gear mechanism according to claim 1, wherein: The worm gear mechanism includes a housing for accommodating the worm and the worm wheel. The grease supply portion includes a support portion that supports the end portion of the grease receiving portion and is formed integrally with the grease receiving portion. The support portion is fixed to the housing so as to overlap with the housing.

3. The worm gear mechanism according to claim 2, wherein: The housing includes a box having an opening and a cover for closing the opening. The support portion is fixed to the cover.

4. The worm gear mechanism according to claim 1, wherein: The grease receiving portion includes a guide end portion closest to the meshing portion and an end face approaching portion linearly arranged from the guide end portion along the end face of the worm wheel. Assuming that the plane including the rotation axis of the worm wheel and the meshing portion is a reference plane, The end surface approach portion is arranged to be inclined with respect to the reference plane when viewed from a direction along the rotation axis of the worm wheel.

5. The worm gear mechanism according to claim 1, wherein: The grease receiving portion includes a grease receiving body portion, the grease receiving body portion including a guide end portion closest to the meshing portion and arranged in a manner standing relative to the end surface of the worm wheel. Assuming that the plane including the rotation axis of the worm wheel and the meshing portion is a reference plane, The grease receiving body includes an inclined portion, and the inclined portion is arranged to be inclined in a direction away from a reference plane with respect to a vertical direction of the end surface of the worm wheel.

6. The worm gear mechanism according to any one of claims 1 to 5, wherein: The grease supply portion includes a fragile portion that is fragile than surrounding portions of the grease supply portion.

7. The worm gear mechanism according to claim 6, wherein: The fragile portion is provided at an end portion of the grease receiving portion or the grease receiving portion.

8. The worm gear mechanism according to claim 1, wherein: The worm gear mechanism includes a second grease supply portion, which is provided at a position where it can contact the grease adhered to the end surface of the worm gear when the worm gear rotates and receive the grease, and the second grease supply portion supplies the received grease to the meshing portion. Assuming that the plane including the rotation axis of the worm wheel and the meshing portion is a reference plane, The grease supply portion is located on one side with the reference surface as a boundary. The second grease supply portion is located on the other side with the reference surface as a boundary.

9. The worm gear mechanism according to claim 8, wherein: The second grease supply portion has a symmetrical shape with respect to the reference plane.

10. The worm gear mechanism according to claim 9, wherein: The grease supply portion and the second grease supply portion are integrated, and when viewed from a direction along the rotation axis of the worm wheel, the grease supply portion and the second grease supply portion are annular so as to surround the rotation axis.

11. An electric power steering device comprising: a worm gear that is rotated by a driving force generated by an electric motor; a worm gear meshing with the worm gear to transmit the driving force of the electric motor to the steering rack; and a grease supply portion configured to supply grease adhering to the end face of the worm wheel to the meshing portion where the worm wheel and the worm are most deeply meshed with each other when the end face of the worm wheel is viewed from a direction along the rotation axis of the worm wheel, The grease supply portion has a grease receiving portion, which is arranged at a position where it can contact the grease attached to the end surface of the worm wheel when the worm wheel rotates and receive the grease. The grease receiving portion supplies the received grease to the meshing portion.

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