Sliding surface sealing structure, gearbox, and motor unit

Abstract

This sliding surface sealing structure (10) is a structure for sealing the sliding surfaces of a rotating member (5) that rotates about an axis and a sealing member (8) in sliding contact with a peripheral surface (5e) of the rotating member (5), the structure comprising: a wall surface (11) that sandwiches the sealing member (8) between the wall surface and the peripheral surface (5e) of the rotating member (5); a facing surface (12) that faces the sealing member (8) across a gap; and a protrusion (13) protruding from the facing surface (12) toward the sealing member (8).

Description

Sealing structure for sliding surface, gear box and motor unit

[0001] The present invention relates to a structure for sealing the sliding surfaces between a rotating member and a sealing member, a gear box having this structure, and a motor unit having this gear box.

[0002] Conventionally, there has been known a structure in which a sealing member such as an O-ring or a packing is applied to the circumferential surface of a rotating member that rotates about an axis to seal a gap between the rotating member and another member. For example, Patent Documents 1 and 2 disclose a structure in which a seal material (sealing member) is applied to the circumferential surface of a gear (rotating member) to seal a gap between the gear and a cover of a case (gear case, gear box).

[0003] Japanese Patent No. 5563885 Japanese Patent Application Laid-Open No. 2023-92172

[0004] However, when the rotating member rotates, the sealing member slides against the circumferential surface of the rotating member. This can cause the sealing member to shift from its predetermined position due to the force acting on the sliding surface between the rotating member and the sealing member. As a result, if the sealing member contacts an inappropriate location, it may cause abnormal noise and wear and deterioration of the sealing member. Furthermore, if the sealing member contacts an inappropriate portion of the rotating member, it may cause a decrease in torque or rotation of the rotating member. These issues can occur in any device or product that includes a rotating member and a sealing member, regardless of whether it is a motor product like those described in Patent Documents 1 and 2.

[0005] The present invention has been devised in view of the above-mentioned problems, and one of its objectives is to prevent the positional displacement of the sealing member. However, the present invention is not limited to this objective. Another objective of the present invention is to achieve the effects that are derived from the configurations shown in the below-described embodiments of the invention, and that cannot be obtained by conventional techniques.

[0006] The present invention can be realized as the embodiments (application examples) disclosed below, which solve at least part of the above-mentioned problems. Each embodiment from embodiment 2 onwards is an embodiment that can be selected as an additional option, and each embodiment can be omitted. None of the embodiments from embodiment 2 onwards discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed sliding surface sealing structure is a structure for sealing the sliding surface between a rotating member that rotates around an axis and a sealing member that is in sliding contact with the circumferential surface of the rotating member, and is characterized by including: a wall surface that sandwiches the sealing member between the circumferential surface of the rotating member, an opposing surface that faces the sealing member with a gap between it and the opposing surface, and a convex portion that protrudes from the opposing surface toward the sealing member.

[0008] Aspect 2. In Aspect 1 above, it is preferable that the sealing member is annular, and that the plurality of protrusions are arranged intermittently along the circumferential direction of the sealing member. Aspect 3. In Aspect 2 above, it is preferable that a lubricant is applied to the sliding surface in advance, or that the sealing member is pre-impregnated with a lubricant. Aspect 4. In any of Aspects 1 to 3 above, it is preferable that the opposing surface faces the sealing member from one side in the axial direction along which the shaft extends, and that the protrusions have a shape in which, when viewed from the shaft center side, two sides formed by each of two surfaces extending from the opposing surface and spaced apart from each other and a flat surface facing the sealing member are rounded.

[0009] Aspect 5. In any of Aspects 1 to 4 above, it is preferable that the opposing surface faces the sealing member from one side in the axial direction along which the axis extends, the rotating member has an end face that is located between the opposing surface and the sealing member in the axial direction and forms a side with the circumferential surface, and the convex portion protrudes beyond the end face of the rotating member to the sealing member side. Aspect 6. In any of Aspects 1 to 5 above, it is preferable that the opposing surface faces the sealing member from one side in the axial direction along which the axis extends, and the convex portion has a reverse tapered shape in which the top surface facing the sealing member is inclined toward the opposing surface as it approaches the wall surface.

[0010] Aspect 7. A disclosed gearbox includes the sliding surface sealing structure according to any one of Aspects 1 to 6 above, a gearbox body having a bottomed cylindrical housing portion that houses a gear as the rotating member, and a cover that seals the housing portion of the gearbox body, wherein the cover has the wall surface, the opposing surface, and the convex portion.

[0011] Aspect 8. The disclosed motor unit includes the gearbox according to aspect 7 above, a helical gear as the gear, a worm built into the gearbox and meshing with the helical gear, and a motor attached to the gearbox and having a rotating shaft connected to the worm.

[0012] According to the present invention, since the convex portion is provided in the sealing structure so as to protrude from the opposing surface toward the sealing member, the position of the sealing member can be regulated by the convex portion, thereby preventing the sealing member from shifting due to sliding contact with the circumferential surface of the rotating member.

[0013] 1 is a plan view of a motor unit according to an embodiment; FIG. 2 is an axial cross-sectional view (cross-sectional view taken along the arrows A-A in FIG. 1) of a reducer and a gear box provided in the motor unit of FIG. 1; FIG. 3 is a cross-sectional view (enlarged view of part III in FIG. 2) illustrating a sealing structure of a sliding surface provided in the gear box of FIG. 2; FIG. 4 is a perspective view of a cover provided in the gear box of FIG. 2, seen from the inside (the lower side in FIG. 2); FIG. 5 is an enlarged view of a protrusion provided in the cover of FIG. 4 (enlarged view of part V in FIG. 4); and FIG. 6 is a cross-sectional view (corresponding to FIG. 3) illustrating a sealing structure of a sliding surface according to a modified example.

[0014] A sliding surface sealing structure, a gear box, and a motor unit will be described as embodiments with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or applications of techniques not explicitly described in the following embodiments. The configurations of the present embodiments can be modified in various ways without departing from the spirit of the invention. Furthermore, they can be selected or combined as needed.

[0015] A sealing structure for a sliding surface (hereinafter simply referred to as a "sealing structure") is a structure that seals the sliding surface between a rotating member that rotates around an axis and a sealing member that is in sliding contact with the circumferential surface of the rotating member. The sliding surface refers to both the circumferential surface of the rotating member and the surface of the sealing member that contacts it. When the rotating member is stationary, there is no "sliding" contact, but these surfaces are called sliding surfaces regardless of the movement (operation or stop) of the rotating member. The expression "surface" in this sliding surface naturally includes shapes (two-dimensional shapes) that are generally recognized as surfaces, such as flat and curved surfaces, and does not intend to exclude three-dimensional shapes and their portions that have steps, unevenness, etc. In other words, the sliding surface may be a structure that has steps, unevenness, etc.

[0016] This sealing structure includes a wall surface that sandwiches a sealing member between itself and the circumferential surface of a rotating member, an opposing surface that faces the sealing member with a gap therebetween, and a protrusion that protrudes from the opposing surface toward the sealing member. In this embodiment, a sealing structure applied to a gear box that houses a gear as a rotating member will be described as an example. In addition, this embodiment will exemplify a case in which the gear as the rotating member is a helical gear of a reducer, and the gear box to which the sealing structure is applied houses the reducer in a motor unit that combines the reducer and a motor.

[0017] [1. Configuration] [1-1. Overall Configuration] Fig. 1 is a plan view of a motor unit 1 according to this embodiment (as viewed from the axial direction of the output gear 6 of the reduction gear 3). The motor unit 1 is used, for example, as a drive source for a vehicle sliding door closer device or a power window device. The motor unit 1 includes a motor 2 having a rotor and a stator (not shown) built into a housing 2A, a reduction gear 3 that reduces the rotational speed of the motor 2, and a gear box 4 that houses the reduction gear 3. The motor 2 of this embodiment is, for example, a DC motor with brushes, and has a rotating shaft 2B that extends to the gear box 4. The motor 2 is attached to the gear box 4 to form a unit with the reduction gear 3.

[0018] The reducer 3 includes a worm 7 connected to the rotating shaft 2B of the motor 2, a helical gear 5 (gear) as a rotating member that meshes with the worm 7, and an output gear 6 for transmitting output to the outside. The worm 7 is a gear that rotates integrally with the rotating shaft 2B of the motor 2. The center of rotation S of the worm 7 coincides with the center line of the rotating shaft 2B of the motor 2. The worm 7 is housed in the gear box 4.

[0019] The helical gear 5 rotates around an axis C perpendicular to the rotation center S of the worm 7 when rotation of the motor 2 is transmitted to the helical gear 5 via the worm 7. The helical gear 5 is a resin gear formed, for example, by injection molding. As shown in FIG. 2 , the helical gear 5 has a substantially annular rim 5b on which external teeth 5a are formed, a substantially annular hub 5c having a smaller diameter than the rim 5b, and an intermediate portion 5d connecting the rim 5b and the hub 5c. Both the rim 5b and the hub 5c are centered on the axis C.

[0020] The output gear 6 is provided coaxially with the helical gear 5 (on the axis C) and rotates integrally with the helical gear 5 about the axis C. In this embodiment, the helical gear 5 and the output gear 6 are provided integrally. However, the helical gear 5 and the output gear 6 may be provided separately from each other and fixed to each other so as to rotate integrally.

[0021] The helical gear 5 and the output gear 6 are aligned in an axial direction D1 along which the axis C extends. The dimensions in a radial direction D2 (the radial direction D2 of the helical gear 5 and the output gear 6) perpendicular to the axial direction D1 gradually decrease in the order of the rim 5b of the helical gear 5, the hub 5c, and the output gear 6. Therefore, the hub 5c of the helical gear 5 forms a step between the rim 5b and the output gear 6. The detailed structure of the step of the hub 5c will be described later.

[0022] The gearbox 4 is made of, for example, resin and includes a gearbox body 4A as a main body that houses the worm 7, helical gear 5, etc., and a cover 4B as a lid that is attached to the gearbox body 4A. As shown in FIG. 1 , the gearbox body 4A has a worm housing portion 41 that houses the worm 7 and a cylindrical, bottomed helical gear housing portion 42 (housing portion) that houses the helical gear 5. These two housing portions 41, 42 communicate with each other at the location where the worm 7 and the helical gear 5 mesh. The worm housing portion 41 extends along the rotation center S of the rotation shaft 2B and the worm 7, and has an opening (not shown) formed in the surface on which the motor 2 is attached. This opening is closed when the housing 2A of the motor 2 is attached.

[0023] As shown in FIG. 2 , the helical gear accommodating portion 42 has an accommodating space surrounded by a bottom portion 44 extending in the radial direction D2 around the axis C of the helical gear 5 and a substantially cylindrical wall portion 45 extending from the outer periphery of the bottom portion 44. The helical gear accommodating portion 42 has an opening 43 surrounded by the end of the wall portion 45 on the side opposite the bottom portion 44 (one side in the axial direction D1, hereinafter referred to as the "upper side"). The opening 43 has the same shape as the bottom portion 44, and in this example, the opening 43 is substantially circular. The helical gear accommodating portion 42 also has a support shaft 46 that protrudes in a substantially cylindrical shape from the center of the bottom portion 44 along the axial direction D1. The support shaft 46 protrudes upward from the opening 43 and rotatably supports the helical gear 5 and the output gear 6.

[0024] The cover 4B is attached to cover the opening 43 of the helical gear housing 42. Because the cover 4B is a fixed member that does not rotate, it is provided so as not to come into contact with the rotating helical gear 5 and output gear 6. The cover 4B has an outer shape similar to that of the opening 43 of the helical gear housing 42, but is slightly larger than the opening 43 and is sized to overlap the wall portion 45 of the helical gear housing 42. In this embodiment, the cover 4B has a circular outer shape. The outer periphery 49 of the cover 4B is attached to the upper end surface of the wall portion 45 of the helical gear housing 42 via a gasket (not shown). This seals the helical gear housing 42. Note that if the cover 4B is attached to the helical gear housing 42 by ultrasonic welding, a gasket is not required.

[0025] The cover 4B has a circular output hole 47 formed in the center of the surface covering the opening 43. The output hole 47 is a through-hole that allows the support shaft 46 and output gear 6 to protrude to the outside of the gearbox 4. In other words, the cover 4B of this embodiment does not completely cover the opening 43 of the helical gear housing 42, and a gap can be formed when the support shaft 46 and output gear 6 are inserted through the output hole 47. The cover 4B sandwiches an O-ring 8 between the helical gear 5 and an inner peripheral portion 48 that surrounds the output hole 47. Note that the surface covering the opening 43 of the cover 4B of this embodiment (the intermediate portion between the inner peripheral portion 48 and the outer peripheral portion 49) is not flat but protrudes toward the helical gear housing 42 and is recessed when viewed from the outside.

[0026] The O-ring 8 is a sealing member for sealing the gap between the helical gear 5 and the cover 4B (inner peripheral portion 48). The O-ring 8 prevents foreign matter from entering the helical gear accommodating portion 42 even if a gap is formed in the output hole 47. The O-ring 8 in this embodiment is annular and is disposed coaxially with the helical gear 5 (on the axis C). The O-ring 8 is made of, for example, rubber and has elasticity. In this embodiment, an O-ring 8 having a circular axial cross section is illustrated, but the cross-sectional shape of the O-ring 8 along the axial direction is not limited to a circular shape and may be, for example, an elliptical shape or a polygonal shape.

[0027] [1-2. Main Configuration] The sealing structure 10 applied to the gearbox 4 will be described in detail below with reference to Figures 3 to 5. In the following description, in the axial direction D1 of the helical gear 5, the side where the cover 4B is arranged relative to the gearbox main body 4A (one side in the axial direction D1, the above-mentioned "upper side") is referred to as the "lower side," while the opposite side (the side where the gearbox main body 4A is arranged relative to the cover 4B) is referred to as the "lower side." In other words, the cover 4B is arranged above the gearbox main body 4A, and the gearbox main body 4A is arranged below the cover 4B. However, the up-down direction of the sealing structure 10 is not limited to that exemplified here. For example, the axial direction D1 may extend horizontally or obliquely relative to the vertical direction.

[0028] 3, a groove for installing an O-ring 8 is provided in the hub 5c, which forms a step in the helical gear 5. The groove is composed of a peripheral surface 5e extending in the circumferential direction about the axis C and a support surface 5f facing upward. In this embodiment, the peripheral surface 5e has a cylindrical shape facing outward in the radial direction D2, and the support surface 5f has a flat shape extending in the circumferential direction about the axis C and along the radial direction D2.

[0029] The peripheral surface 5e and the support surface 5f form an L-shape that opens outward in the radial direction D2 in a cross section (cross section shown in FIGS. 2 and 3 ) of the axial direction D1 that includes the axis C. The peripheral surface 5e and the support surface 5f define a predetermined position where the O-ring 8 is to be disposed. In other words, when the O-ring 8 contacts both the peripheral surface 5e and the support surface 5f, it can be said that the O-ring 8 is in the predetermined position (no misalignment has occurred).

[0030] The helical gear 5 has an end face 5g located above the support surface 5f (on one side in the axial direction D1) and forming a side 5h (angular edge) with the circumferential surface 5e. Like the support surface 5f, the end face 5g faces upward and is planar, extending along the circumferential direction and the radial direction D2. The end face 5g corresponds to the upper end of the helical gear 5 and smoothly connects to the output gear 6. The end face 5g is located below the inner circumferential portion 48 of the cover 4B. Note that the circumferential surface 5e is not limited to being cylindrical. The support surface 5f and the end face 5g may be planar and inclined with respect to the radial direction D2, or may be gently curved.

[0031] The gearbox 4 includes a sealing structure 10 that seals the sliding surfaces between the helical gear 5 and the O-ring 8. The sliding surfaces here refer to the surfaces where the helical gear 5 and the O-ring 8 slide and contact, and include both the circumferential surface 5e of the helical gear 5 and the inner circumferential surface 8a of the O-ring 8. Grease (lubricant) is applied to these sliding surfaces in advance. Specifically, the O-ring 8 is assembled to the helical gear 5 with grease applied to at least one of the circumferential surface 5e of the helical gear 5 and the inner circumferential surface 8a of the O-ring 8, thereby applying grease to the sliding surfaces. The cover 4B is then attached in this state. Note that instead of applying grease to the sliding surfaces in advance as described above, the O-ring 8 may be impregnated with grease (lubricant) in advance.

[0032] The sealing structure 10 includes a wall surface 11 that sandwiches the O-ring 8 between itself and the peripheral surface 5e of the helical gear 5, an opposing surface 12 that faces the O-ring 8 from above (one side in the axial direction D1), and a protrusion 13 that protrudes from the opposing surface 12 toward the O-ring 8. In this embodiment, the cover 4B has these wall surface 11, opposing surface 12, and protrusion 13. In other words, all of the elements 11 to 13 of the sealing structure 10 are provided on the cover 4B, which is a single component.

[0033] The wall surface 11 extends in the circumferential direction around the axis C so as to face the circumferential surface 5e of the helical gear 5 in the radial direction D2. In this embodiment, the wall surface 11 is a smoothly curved surface (cylindrical inner peripheral surface) that faces inward in the radial direction D2 and extends in the circumferential direction centered on the axis C, and is positioned outward in the radial direction D2 than the circumferential surface 5e of the helical gear 5. The wall surface 11 cooperates with the circumferential surface 5e of the helical gear 5 to sandwich the O-ring 8 from the outside and inside in the radial direction D2. When sandwiched between the wall surface 11 and the circumferential surface 5e in this manner, the elastic O-ring 8 is compressed in the radial direction D2 and deforms in the axial direction D1.

[0034] The opposing surface 12 faces downward (the other side in the axial direction D1) and is disposed with a gap between it and the O-ring 8. The gap between the opposing surface 12 and the O-ring 8 is originally intended to provide a space for the O-ring 8 to properly escape so that deformation of the O-ring 8 in the axial direction D1 does not cause any problems, and also serves as a space to allow for dimensional variations in the axial direction D1 of each component. In this embodiment, the gap between the opposing surface 12 and the O-ring 8 also functions as a space for storing grease (grease reservoir). The opposing surface 12 in this embodiment is flat and extends at least along the radial direction D2 at the inner circumferential portion 48 of the cover 4B.

[0035] On the other hand, the convex portion 13 is a portion that partially protrudes downward from the opposing surface 12 and is formed so as to be in slight contact with the O-ring 8 or to leave a small gap between it and the O-ring 8. The convex portion 13 has the function of preventing the O-ring 8 from shifting upward (floating) from a predetermined position. The convex portion 13 protrudes downward (toward the O-ring 8) from the end face 5g of the helical gear 5 in the axial direction D1. In other words, the top surface 14 of the convex portion 13 that faces the O-ring 8 is located below the end face 5g of the helical gear 5. The top surface 14 may cooperate with the support surface 5f of the helical gear 5 to sandwich the O-ring 8 from above and below in the axial direction D1, or may be positioned to sandwich the O-ring 8 without contacting it.

[0036] In a cross section in the axial direction D1 including the axis C (the cross section shown in FIGS. 2 and 3 ), the wall surface 11 and the top surface 14 form an L-shape that opens inward in the radial direction D2. Furthermore, as shown by the dashed line in FIG. 3 , in a similar cross section at a location where there are no protrusions 13 (between adjacent protrusions 13), the wall surface 11 and the opposing surface 12 also form an L-shape that opens inward in the radial direction D2. However, at a location where a protrusion 13 is present, the L-shape has a shorter dimension in the axial direction D1 by the amount of protrusion of the protrusion 13.

[0037] Fig. 4 is a perspective view of the cover 4B as viewed from the bottom (the side where the helical gear 5 is disposed). As shown in Fig. 4, in this embodiment, a plurality of (e.g., 16) protrusions 13 are intermittently arranged along the circumferential direction of the O-ring 8. Although Fig. 4 indicates only one protrusion 13, the plurality of protrusions 13 may, for example, all be configured in the same manner and be disposed at equal intervals along the circumferential direction of the O-ring 8. In the circumferential direction of the O-ring 8, the distance between adjacent protrusions 13 is ensured to be greater than the dimension of one protrusion 13 (the dimension corresponding to the distance between end side surfaces 15, 15, described below).

[0038] As shown in Figure 5, the protrusion 13 of this embodiment is connected to the wall surface 11 and has three side surfaces 15, 15, 16 extending from the opposing surface 12 and a top surface 14 connecting these side surfaces 15, 15, 16. The three side surfaces 15, 15, 16 are divided into two end side surfaces 15, 15 (two surfaces) spaced apart from each other and an inner side surface 16 connecting the end side surfaces 15, 15 on the inside in the radial direction D2. Both end side surfaces 15, 15 extend along the axial direction D1 and the radial direction D2. In contrast, the inner side surface 16 extends along the axial direction D1 and the circumferential direction and forms sides (angular edges) with each end side surface 15.

[0039] On the other hand, the top surface 14 is a plane extending inward in the radial direction D2 from the wall surface 11, and although it forms a side (a square edge) with the inner surface 16, it is connected to the end side surfaces 15, 15 by a smoothly curved surface. Therefore, when viewed from the axis C side, the convex portion 13 has a shape in which the two sides formed by each of the end side surfaces 15, 15 and the top surface 14 (plane) are rounded (i.e., a semi-cylindrical shape). Note that the convex portion 13 may be provided separated from the wall surface 11 (with a gap between it and the wall surface 11). In this case, the outer surface that pairs with the inner surface 16 is disposed opposite the wall surface 11.

[0040] [2. Actions and Effects] (1) According to the above-described sealing structure 10, the convex portion 13 protrudes from the opposing surface 12 toward the O-ring 8 serving as a sealing member, thereby restricting the position of the O-ring 8. This prevents the O-ring 8 from shifting position (lifting toward the opposing surface 12) due to sliding contact with the circumferential surface 5e of the helical gear 5 serving as a rotating member. This prevents the O-ring 8 from contacting an inappropriate portion (e.g., the edge 5h between the circumferential surface 5e and the end face 5g of the helical gear 5) and improves the wear resistance and durability of the O-ring 8. Furthermore, preventing the O-ring 8 from contacting an inappropriate portion of the rotating helical gear 5 prevents a decrease in torque and rotation of the helical gear 5.

[0041] Incidentally, instead of the structure in which the convex portion 13 protrudes from the opposing surface 12 of a member separate from the helical gear 5 (the cover 4B in this embodiment), as in the above embodiment, it is also possible to provide the helical gear 5 with some kind of structure to prevent misalignment of the O-ring 8. However, in this case, additional processing is required for the helical gear 5, which creates a problem of making the manufacturing of the helical gear 5 more complicated. In contrast, with the above-described sealing structure 10, the convex portion 13 is formed on the cover 4B, which is a separate component from the helical gear 5, to prevent misalignment of the O-ring 8, so no additional processing is required for the helical gear 5. This avoids the need for complicated manufacturing of the helical gear 5.

[0042] (2) If multiple protrusions 13 are arranged intermittently along the circumferential direction of the annular O-ring 8, the position of the O-ring 8 can be regulated at multiple locations along the circumferential direction of the O-ring 8. This makes it possible to more stably prevent misalignment of the annular O-ring 8. Furthermore, if the protrusions 13 are arranged intermittently along the circumferential direction, deformation (sink marks) during molding can be suppressed compared to when the protrusions 13 are formed around the entire circumferential direction and become thick. This improves the dimensional accuracy of the protrusions 13, thereby improving the reliability of the sealing structure 10.

[0043] (3) If grease is applied to the sliding surface in advance or the O-ring 8 is impregnated with grease in advance, the spaces between the discontinuously arranged protrusions 13 (gaps between the opposing surface 12 and the O-ring 8) function as grease reservoirs, allowing grease to be stored between the protrusions 13. This not only makes it possible to prevent the O-ring 8 from shifting position by the protrusions 13, but also improves the lubricity of the sliding surface. In particular, if the distance between adjacent protrusions 13 in the circumferential direction of the O-ring 8 is ensured to be larger than the dimension of one protrusion 13, the spaces between the protrusions 13 can function well as grease reservoirs.

[0044] Furthermore, when the O-ring 8 is displaced in the circumferential direction due to sliding contact with the helical gear 5, the O-ring 8 alternates between portions near the convex portions 13 and portions away from the convex portions 13 along the circumferential direction. This allows grease accumulated between the convex portions 13 to flow in the circumferential direction due to the pumping effect (change in the clearance in the circumferential direction). This also increases the lubricity of the sliding surfaces, thereby suppressing torque and rotational slowdown of the helical gear 5. Furthermore, when the elastic O-ring 8 contacts the convex portions 13 and deforms, the O-ring 8 alternates between portions deformed by the convex portions 13 and portions not in contact with the convex portions 13 along the circumferential direction. This allows grease accumulated between the convex portions 13 to flow in the circumferential direction with a stronger pumping effect. This further increases the lubricity of the sliding surfaces, thereby further suppressing torque and rotational slowdown of the helical gear 5.

[0045] (4) When viewed from the axis C, the convex portion 13 has two rounded sides formed by the end side surfaces 15, 15 extending apart from each other from the opposing surface 12 and the top surface 14 facing the O-ring 8. This effectively suppresses stress concentration when the convex portion 13 contacts the O-ring 8. This contributes to preventing damage to the O-ring 8, particularly when the O-ring 8 moves circumferentially due to sliding contact with the helical gear 5. Furthermore, the flat top surface 14 contacts the O-ring 8, thereby appropriately restricting the position of the O-ring 8 while suppressing stress concentration on the O-ring 8. This prevents damage to the O-ring 8 and suppresses misalignment of the O-ring 8.

[0046] (5) If the protrusion 13 protrudes beyond the end face 5g of the helical gear 5 toward the O-ring 8, the position of the O-ring 8 is restricted by this protrusion 13, thereby preventing the O-ring 8 from contacting the side 5h of the helical gear 5 or getting caught in the gap between the opposing surface 12 and the side 5h of the helical gear 5. This prevents abnormal noise caused by contact between the side 5h of the helical gear 5 and the O-ring 8, and allows the O-ring 8 to properly exhibit its sealing effect (sealing properties).

[0047] (6) The gearbox 4 described above includes the sealing structure 10, a gearbox body 4A for accommodating the helical gear 5, and a cover 4B for sealing the helical gear accommodating portion 42. In this gearbox 4, if the cover 4B has the wall surface 11, the opposing surface 12, and the protrusion 13, all elements of the sealing structure 10 are provided on the cover 4B, which is a single part. Therefore, existing products can be used for the helical gear 5 and the gearbox body 4A, and misalignment of the O-ring 8 can be suppressed as described above while minimizing cost increases with minor modifications.

[0048] (7) According to the motor unit 1 equipped with the gear box 4, the sealing structure 10 is applied to the gear box 4, and therefore, with only a few modifications as described above, it is possible to suppress misalignment of the O-ring 8 and appropriately exert the sealing effect of the O-ring 8. Therefore, it is possible to suppress an increase in cost while ensuring the sealing performance of the cover 4B, thereby improving reliability.

[0049] [3. Other] The above-described protrusion 13 is an example. The sealing structure 10 may include a protrusion 13' shown in FIG. 6 instead of the above-described protrusion 13. The protrusion 13' according to this modification has a top surface 14' facing the O-ring 8 that is inclined toward the opposing surface 12 (upward in the example of FIG. 6) as it approaches the wall surface 11. In other words, the protrusion amount of the protrusion 13' is greatest on the circumferential surface 5e side and decreases as it approaches the wall surface 11. In this manner, the top surface 14' of this modification is formed in a flat shape inclined with respect to the radial direction D2 so as to restrict the O-ring 8 toward the wall surface 11. Note that in FIG. 6, elements that are the same as or correspond to those in the above embodiment are denoted by the same reference numerals, and redundant description will be omitted here.

[0050] According to the convex portion 13' of this modified example, when the convex portion 13' hits the O-ring 8, the inversely tapered top surface 14' can apply a force toward the wall surface 11 to the O-ring 8. This more effectively prevents the O-ring 8 from contacting an inappropriate portion (e.g., the side 5h) other than the circumferential surface 5e of the helical gear 5. This more reliably prevents the generation of abnormal noise and the reduction in torque and rotation of the helical gear 5, and more effectively improves the wear resistance and durability of the O-ring 8.

[0051] The flat top surfaces 14, 14' described above are merely an example. The top surfaces 14, 14' may be formed into a curved shape (a crescent shape when viewed from the axis C) by smoothly extending the curved surface forming the rounded edges between the end side surfaces 15, 15. The protrusions 13, 13' may be rectangular parallelepipeds with edges between each of the end side surfaces 15, 15 and the top surfaces 14, 14', or may be trapezoidal when viewed from the axis C. Furthermore, the protrusions 13, 13' do not have to be equally spaced along the circumferential direction, and only one protrusion may protrude from the opposing surface 12. In either case, by providing the protrusion 13 protruding from the opposing surface 12 facing the O-ring 8 toward the O-ring 8, misalignment of the O-ring 8 can be suppressed as described above.

[0052] The wall surface 11 and the opposing surface 12 are not limited to the above configurations. For example, the wall surface 11 may be inclined with respect to the axial direction D1. Furthermore, the opposing surface 12 is not limited to being opposed to the O-ring 8 from one side in the axial direction D1 (the upper side in FIGS. 2 and 3 ). It may be opposed to the O-ring 8 from the other side in the axial direction (the lower side in FIGS. 2 and 3 ). It may be slightly inclined with respect to the radial direction D2, or may be a curved surface. Furthermore, depending on the shape and positional relationship of the wall surface 11, the opposing surface 12 may be opposed to the O-ring 8 from the radial direction D2. At least, the opposing surface 12 is a surface separate from the wall surface 11 and faces the sealing member (e.g., the O-ring 8) with a gap therebetween.

[0053] The rotating member and sealing member applied to the above-described sealing structure 10 are not limited to the above-described helical gear 5 and O-ring 8. The rotating member may be any member that rotates about an axis, such as a spur gear, or may be a member other than a gear. Furthermore, the sealing member may be any member that makes sliding contact with the circumferential surface of the rotating member, and does not have to be annular or elastic.

[0054] In the above embodiment, the elements 11 to 13 of the sealing structure 10 are provided on the cover 4B, which is a single component, but the elements 11 to 13 of the sealing structure 10 may be provided separately on two or more different components. For example, instead of the convex portion 13 being provided integrally with the opposing surface 12 as described above, a convex portion separate from the opposing surface 12 (a separate component) may be prepared and attached (fixed) to the opposing surface 12, thereby causing the convex portion to protrude from the opposing surface 12. The materials of the helical gear 5 and the gear box 4 are not particularly limited, and do not have to be made of the resin described above.

[0055] In the above embodiment, the sealing structure 10 applied to the gear box 4 of the reducer 3 included in the motor unit 1 has been described, but the above sealing structure 10 may also be applied to the gear box of a standalone reducer 3 that is not unitized with the motor 2, or to the gear box of a device other than the reducer 3. This sealing structure is applicable to various structures (devices and equipment) in which a sealing member seals between a rotating member and a non-rotating member, and may be applied to home appliances, for example.

[0056] DESCRIPTION OF SYMBOLS 1 Motor unit 2 Motor 2B Rotating shaft 3 Reducer 4 Gear box 4A Gear box body 4B Cover 5 Helical gear (gear, rotating member) 5e Circumferential surface 5g End surface 7 Worm 8 O-ring 10 Sealing structure 11 Wall surface 12 Opposing surface 13 Convex portion 14 Top surface 15 End side surface (two surfaces) 42 Helical gear accommodating portion (accommodating portion) C Axis center of helical gear D1 Axial direction

Claims

1. A structure for sealing a sliding surface between a rotating member which rotates about an axis and a sealing member which is in sliding contact with the peripheral surface of the rotating member, comprising: a wall surface which holds the sealing member between the peripheral surface of the rotating member, an opposing surface which faces the sealing member with a gap therebetween, and a convex portion which protrudes from the opposing surface towards the sealing member.

2. The sealing structure for a sliding surface according to claim 1, characterized in that the sealing member is annular, and a plurality of the protrusions are intermittently arranged along the circumferential direction of the sealing member.

3. The sealing structure for a sliding surface according to claim 2, characterized in that a lubricant is applied to the sliding surface in advance, or the sealing member is impregnated with a lubricant in advance.

4. A sealing structure for a sliding surface as described in claim 1, characterized in that the opposing surface faces the sealing member from one side in the axial direction along which the shaft center extends, and the convex portion has a shape in which two sides formed by each of two surfaces extending from the opposing surface and spaced apart from each other and a plane facing the sealing member are rounded when viewed from the shaft center side.

5. A sealing structure for a sliding surface as described in claim 1, characterized in that: the opposing surface faces the sealing member from one side in the axial direction along which the shaft center extends; the rotating member has an end surface that is located between the opposing surface and the sealing member in the axial direction and forms an edge with the circumferential surface; and the convex portion protrudes further toward the sealing member than the end surface of the rotating member.

6. A sealing structure for a sliding surface as described in claim 1, characterized in that said opposing surface faces said sealing member from one side in the axial direction along which said shaft center extends, and said convex portion has a top surface facing said sealing member that is inclined toward said opposing surface as it approaches said wall surface, forming an inverse tapered shape.

7. A gearbox comprising: a sealing structure for a sliding surface as claimed in any one of claims 1 to 6; a gearbox body having a bottomed cylindrical storage section for storing a gear as the rotating member; and a cover for sealing the storage section of the gearbox body, wherein the cover has the wall surface, the opposing surface, and the convex portion.

8. A motor unit comprising: a gearbox as claimed in claim 7; a helical gear as said gear; a worm built into said gearbox and meshing with said helical gear; and a motor attached to said gearbox and having a rotating shaft connected to said worm.

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