Method for fitting lid onto opening part of power steering system and lid
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-05-29
- Publication Date
- 2026-03-30
AI Technical Summary
Existing methods for attaching lids to power steering system cases are cumbersome, require additional parts, and lack visual confirmation of proper insertion, leading to increased manufacturing complexity and cost.
A method using an O-ring seal within annular grooves on the lid and case to elastically clip the lid in place, eliminating the need for additional components like clips or screws, ensuring airtight closure.
Simplifies the attachment process, reduces manufacturing complexity, and maintains a hermetic seal with improved tightness and pressure resistance.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to the field of cases for automotive power steering systems, and more particularly to an assembly relating to the case, a lid on the case, and a method for mounting the lid on the case. [Background technology]
[0002] A motor vehicle includes a steering system with a steering wheel that drives a steering column. The steering column is connected to a steering box with a rack that extends along a transverse axis connecting the vehicle's two steered wheels. The rack allows the vehicle's wheels to turn through rotation of the steering wheel.
[0003] The power steering system also includes an assist device that applies an assist force to the rack in response to the force applied by the driver to the steering wheel, thereby reducing the force required by the driver to turn the steering wheel.
[0004] Known electrical auxiliary devices include an electric motor connected to a reducer with a case fixed to the motor, a worm gear, and a worm wheel mounted on a shaft driven by the worm gear and connected to a pinion that meshes with a rack.
[0005] Such cases typically include one or more mounting seats that define an access opening through the outer wall of the case to allow for the introduction and assembly of all or part of the elements of the reducer. The access opening must be closed by a lid, typically provided with a seal, e.g., an annular seal, to prevent the ingress of liquids or foreign matter such as gravel or dust into the case, thereby ensuring proper operation of the reducer.
[0006] According to known solutions, the lid is attached to the case by means of a clip carried by the lid. The clip fits into a groove machined into the case at the periphery of the inner surface of the opening. The use of such a lid has the disadvantage that the correct insertion of the clip into the groove cannot be visually controlled. This makes it impossible to verify the correct insertion and proper retention of the lid. Furthermore, the presence of a clip on the lid involves an additional risk of breakage and requires additional manufacturing operations, which increase production costs.
[0007] According to a known solution, the lid is attached to the case by screws that engage mounting projections on the lid and holes drilled into bosses located on the case. This solution is unsatisfactory because it requires additional components, namely, screws, bosses on the case, and projections drilled into the periphery of the lid. The mounting projections can also cause space issues and may not be compatible with the space available in the power steering system. Furthermore, limiting the number of screw attachment points to two can cause deformation of the lid at high temperatures. This solution also requires additional manufacturing operations to fasten the lid to the case. Summary of the Invention [Problem to be solved by the invention]
[0008] Therefore, simplifying the process of attaching the lid to the case and reducing the number of parts required for this purpose is desirable for closing the opening formed in the case in a sealed manner. Also, to simplify the manufacturing and machining of these parts, it is desirable to simplify the shape of the lid and case while still ensuring the airtightness of the closure of the case by the lid. Also, for cost reasons, it may be desirable to make the lid from the lowest cost plastic material. [Means for solving the problem]
[0009] An embodiment relates to a method for attaching a lid to an opening formed in a power steering case, the method including the steps of: inserting the lid into the opening of the case until an O-ring seal disposed in a first annular groove formed in a first inner wall of one of the lid and the case contacts a frusto-conical portion of a second inner wall of the other of the lid and the case; and applying pressure to the lid over the opening of the case, gradually compressing the O-ring seal over the frusto-conical portion until a closed position of the lid is reached in which the O-ring seal attempts to return to its less deformed shape within a second annular groove formed in a second inner wall opposite the first annular groove.
[0010] Thanks to these configurations, the resilience of the seal is used to clip the lid to the case, thus avoiding the need to form additional elements on the lid and case, such as clips, protrusions and threaded bosses, simplifying the case closing operation while ensuring tightness of the case closure.
[0011] According to one embodiment, the lid is formed with a first inner wall and the case is formed with a second inner wall, or the case is formed with a first inner wall and the lid is formed with a second inner wall.
[0012] Thus, the seal can be located within the case or on the lid, as required.
[0013] According to one embodiment, when the lid is in the closed position, the peripheral rim of the lid abuts against the annular edge of the opening in the case, and / or the inner wall of the lid abuts against the frusto-conical portion of the case, and / or one end of the inner wall of the lid abuts against an annular shoulder formed by the inner wall of the case.
[0014] The provision of the abutment prevents the lid from being pushed into the case beyond the closed position.
[0015] According to one embodiment, the seals in the first and second annular grooves are held elastically deformed in the closed position of the lid.
[0016] This configuration makes it possible to ensure a good seal of the closure of the case as well as to maintain the lid's resistance to constant pressure ejection.
[0017] According to one embodiment, the seal has a cross section dimensioned to hold the lid in the closed position against a pressure differential of 35 kPa between the interior and exterior of the case.
[0018] Thus, the pressure resistance for retaining the lid over the opening of the case can be adjusted by adjusting the cross-sectional dimensions of the seal and, therefore, the cross-sectional dimensions of the groove for accommodating the seal.
[0019] An embodiment also relates to a power steering case including an opening in the case, a lid configured to close the opening, and an O-ring seal disposed in a first annular groove formed in a first inner wall of one of the lid and the case, wherein a second inner wall of the other of the lid and the case has a frusto-conical portion configured to gradually compress the seal until it reaches a closed position in which it tends to again resume its less deformed initial shape in a second annular groove formed in the second inner wall opposite the first annular groove.
[0020] According to one embodiment, the lid is formed with a first inner wall and the case is formed with a second inner wall, or the case is formed with a first inner wall and the lid is formed with a second inner wall.
[0021] According to one embodiment, the lid comprises a peripheral rim configured to abut the edge of the opening of the case when the lid is in the closed position.
[0022] According to one embodiment, the first annular groove is deeper than the second annular groove.
[0023] According to one embodiment, the first annular groove and the second annular groove are shaped to accommodate between 70% and 75% of the seals in the first annular groove and between 30% and 25% of the seals in the second annular groove, respectively.
[0024] These ratios make it possible to ensure sufficient retention of the seal on the lid, and in particular of the seal in the lid or case, during the insertion and removal operations of the lid on the case.
[0025] According to one embodiment, the seal has a cross section dimensioned to hold the lid in the closed position despite a pressure differential of 35 kPa between the interior and exterior of the case.
[0026] According to one embodiment, the truncated cone-shaped portion has a flare angle of 15° to 30° relative to the insertion direction of the lid into the opening of the case.
[0027] These slope values of the frustoconical portion allow the seal to be compressed gradually enough to prevent tearing or damage.
[0028] According to one embodiment, the groove formed in the case is offset towards the inside of the case by a distance of at least 0.3 mm and at most 0.8 mm.
[0029] This configuration makes it possible to obtain a constant closing pressure of the lid on the case. [Brief explanation of the drawings]
[0030] The present invention will be better understood through the following description and with reference to the accompanying figures, in which like reference numbers correspond to structurally and / or functionally identical or similar elements. [Figure 1] 1 is a perspective view showing a part of a power steering system for an automobile; [Figure 2] FIG. 1 is a perspective view of a part of a case and a cover of a conventional power steering device. [Figure 3] FIG. 2 is a schematic cross-sectional view of a portion of the case and the lid. [Figure 4] FIG. 1 is a perspective view of a case of a power steering system closed by a lid according to one embodiment. [Figure 5] FIG. 1 is a front view of a lid on a case, according to one embodiment. [Figure 6] FIG. 1 is a cross-sectional view of a lid on a case according to one embodiment. [Figure 7A] FIG. 10 is a more detailed cross-sectional view of the edge of the lid in a closed position over the case opening, according to one embodiment. [Figure 7B] FIG. 10 is a more detailed cross-sectional view of the edge in a position prior to the closed position on the case opening, according to one embodiment. [Figure 8A] FIG. 10 is a more detailed cross-sectional view of the edge of the lid in a closed position over the case opening according to another embodiment. [Figure 8B] 10 is a more detailed cross-sectional view of the edge of the lid in a position before the closed position on the case opening according to another embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION
[0031] 1 shows a dual-pinion on-rack power steering system 1, which comprises a steering shaft 2 connected at one end to a steering wheel and at the other end to a rack 3 by a first pinion, and an assist motor 4 connected to the rack 3 via a reducer housed in a case 5 and also connected to the rack 3 via a second pinion. The case 5 is closed by a lid 6 which allows access to, among other things, a worm wheel with a worm screw housed within the case 5.
[0032] 2 and 3 show a portion of the lid 6 and the case 5 to which the lid is engaged. The circular lid 6 is attached to the case 5 by screws 9 that engage with protrusions 8 formed on the periphery of the lid 6. The screws 9 are tightened into holes in bosses 7 formed on the case 5. In FIG. 3, the lid 6 has a cylindrical portion 6a that is adapted to engage within a complementary opening 5a formed in the case 5. The cylindrical portion 6a of the lid has an annular groove 6b between the cylindrical portion 6a of the case 5 and the opening 5a for receiving an O-ring seal 10 that ensures a tight seal.
[0033] This closed case design is desirable because it simplifies both the number of parts required and the machining and manufacturing operations.
[0034] 4 to 6 show the lid 30 closing the opening 20a of the case 20. The case 20 can house a reducer having a worm screw and a worm wheel and includes an interface 11 for coupling to a motor. In this application, the lid 30 closes the opening for access to the worm wheel of the reducer.
[0035] Figures 7A and 7B show the edge of a lid in a closed position and a position prior to the closed position, respectively, over a case opening 20a, according to one embodiment. Figures 6, 7A, and 7B specifically show a case 20 and a case opening 20a having a substantially cylindrical inner wall 21 adjacent a circular edge 23. The lid 30 includes a cylindrical wall 31 having a shape complementary to the shape of the inner wall 21 of the case 20. The lid 30 includes a peripheral rim 33 adapted to rest against the edge 23 of the case opening 20a when the lid 30 is closing the case opening 20a.
[0036] According to one embodiment, the inner wall 21 of the case 20 and the cylindrical wall 31 of the lid 30 are provided with annular grooves 22, 32, respectively, that are positioned opposite each other when the lid 30 is in the closed position. The grooves 22, 32 are shaped to receive an O-ring seal 40.
[0037] According to one embodiment, the inner wall 21 of the case 20 has, between the edge 23 and the groove 22, a frustoconical portion 24 that widens toward the edge 23. This causes the opening 20a in the case 20 to have a narrower cross-section between the frustoconical portion 24 and the groove 22. The frustoconical portion 24 is shaped so that the lid 30 can be easily introduced into the case 20 until the seal 40 abuts against the frustoconical portion 24. The closing abutment of the lid 30 can be reached when the rim 33 contacts the edge 23 by applying pressure to the lid 30 to urge the seal 40, which elastically deforms (FIG. 7B) across the small diameter end 25 of the frustoconical portion 24 and into the groove 22 of the case 20 (FIG. 7A), where the seal 40 tends to return to its initial, undeformed shape. Thus, just before the lid 30 reaches its closed position, the seal 40 reaches a maximum deformation and then returns to a less deformed configuration within the grooves 22, 32. In this way, the lid 30 is clipped onto the case 20 in the closed position.
[0038] These configurations allow the lid 30 to close the case 20 in a sealed manner and be securely held in its closed position without the need for additional closure elements such as clips or screws associated with the projections on the lid and the threaded bosses on the case.
[0039] According to one embodiment, groove 22 may be slightly offset toward the inside of case 20 relative to groove 32, for example by a distance of 0.3 mm to 0.8 mm, to accommodate gaps and ensure that when lid 30 is pressed against opening 20a of the case, rim 33 of the lid then abuts edge 23 of the opening. Thus, in the closed position, smaller diameter end 25 of frustoconical portion 24 slightly compresses seal 40.
[0040] To ensure the tightness of the closure performed by the lid 30, the seal 40 remains compressed within the grooves 22,32.
[0041] According to one embodiment, the seal 40 may be pre-attached to the lid 30 when the lid 30 is engaged with the case 20. To this end, the groove 32 may be deeper than the groove 22.
[0042] According to one embodiment, between 70% and 75% of the seal 40 is contained in the groove 32 of the lid, and between 30% and 25% of the seal 40 is contained in the groove 22 of the case. Therefore, the seal 40 can be retained within the groove 32 and can traverse the small diameter end 25 of the frustoconical portion 24 to reach the groove 22 without being torn off or damaged. Furthermore, the cross-sectional dimensions of the seal 40 can be determined so that the lid 30 can remain in the closed position even when a pressure difference of 35 kPa between the inside and outside of the case 20 occurs, causing the internal pressure to exceed the external pressure. Increasing the percentage of the seal 40 contained within the groove 22 also increases the lid 30's resistance to exhaust pressure from the case 20.
[0043] According to an exemplary embodiment, the flare angle of the frustoconical portion 24 of the case (relative to the direction of insertion of the lid into the case) is configured to be greater than or equal to 15 degrees and less than or equal to 30 degrees. In this way, the seal 40 can be gradually compressed enough to avoid being torn from or damaged by the groove 32.
[0044] According to one exemplary embodiment, the lid 30 is outwardly domed (FIG. 6).
[0045] According to one exemplary embodiment, the exterior surface of the lid 30 has radial ribs 35 extending from the edge 33 toward the center and the lid (FIGS. 4 and 5). These ribs can provide reinforcement to the lid.
[0046] According to various exemplary embodiments, the lid 30 has a circular (FIGS. 4, 5), oval, elliptical, egg-shaped, or elliptical shape.
[0047] According to various examples, the lid 30 is molded or machined from metal or plastic. The plastic material used may be polypropylene.
[0048] The cross-section of the grooves 22, 32 can have a variety of shapes, such as a rectangular shape, provided that the volume bounded by opposing grooves 22, 32 is sufficient to accommodate the thermal and chemical deformation and expansion of the seal 40.
[0049] 8A and 8B show the edge of the lid 60 and a portion of the case 50 in a closed position over the opening 50a of the case 50, respectively, prior to the closed position, according to one embodiment. In this embodiment, the lid 60 and case 50 differ from those shown in FIGS. 7A and 7B , particularly in that the frustoconical portion 64 is formed not by the inner wall of the case, but by the inner wall 61 of the lid 60 between a groove 62 formed in the inner wall 61 and a lower edge 66 of the inner wall of the lid 60. This gives the opening 50a in the case 50 a generally cylindrical shape with the annular groove 52 into which the O-ring seal 40 is inserted. The frustoconical portion 64 is shaped to allow the lid 60 to be easily inserted into the case 50 until the frustoconical portion 64 abuts the seal 40. In this embodiment, the lid 60 may also include a rim 63 that, together with the edge 53 of the case, forms a closing abutment for the lid 60. This closure abutment can be reached as described above by applying pressure to the seal 40 to force it across the larger-diameter end 65 of the frustoconical portion 64 by elastically deforming ( FIG. 8B ) until it reaches the groove 62 of the lid 60, where the seal 40 tends to have its initial, undeformed shape ( FIG. 8A ). Thus, just before the lid 60 reaches its closed position, the seal 40 reaches its maximum deformation and then returns to a less deformed form within the grooves 52, 62. In this way, the lid 60 is also clipped onto the case 50 in the closed position. To ensure that a seal is maintained, particularly within the groove 52, upon insertion of the lid 60, the groove 52 can be deeper than the groove 62. Furthermore, the groove 52 can have a narrower section, e.g., a dovetail-shaped section, for retaining the seal.
[0050] Also, groove 52 is slightly offset relative to groove 62, e.g., by a distance of 0.3 mm to 0.8 mm, toward the inside of the case to accommodate any gaps and ensure that the lid is pressed against case opening 50a and that rim 63 of the lid then abuts against opening edge 53. Thus, in the closed position, reduced diameter end 65 of frustoconical portion 64 slightly compresses seal 40.
[0051] The seal 40 remains compressed within the grooves 52, 62 to ensure a tight closure effected by the lid.
[0052] According to one embodiment, 70% to 75% of the seal is contained within the groove 52 of the case, and 30% to 25% of the seal is contained within the groove 62 of the lid. Therefore, the seal 40 can be retained within the groove 52, allowing the smaller diameter end 65 of the frustoconical portion 64 to pass across the seal 40 without the seal 40 being torn from the groove 52 or damaged. Furthermore, the cross-sectional dimensions of the seal 40 can be determined so that the internal pressure is greater than the external pressure, allowing the lid 60 to remain in the closed position even when the pressure difference between the inside and outside of the case 50 is 35 kPa. Increasing the percentage of the seal 40 contained within the groove 62 also increases the lid 60's resistance to exhaust pressure from the case 50.
[0053] According to an exemplary embodiment, the flare angle of the frustoconical portion 64 of the lid 60 (relative to the direction of insertion of the lid into the case) is configured to be greater than or equal to 15° and less than or equal to 30°, so that the seal 40 can be gradually compressed sufficiently to avoid being torn from or damaged by the groove 52.
[0054] It will be apparent to those skilled in the art that the present invention is subject to various implementations and various applications, and in particular is not limited to cases housing reduction gears for automotive power steering systems, but is more generally applicable to power steering cases having an opening sealed and closed by a lid.
[0055] The case opening and lid 30, 60 do not necessarily have to be circular or oval in shape, but may have any other rounded shape that may allow a seal to be provided that provides a tight seal. The seal may be molded to fit the contours of the case opening.
[0056] The abutment formed by the rims 33, 63 of the lids 30, 60 can be omitted. In fact, the inner wall 31 of the lid 30 can be shaped to match the shape of the frustoconical portion 24 of the case, and abuts against the frustoconical portion 24 when the lid is in the closed position. The abutment can also be provided by an annular shoulder 26, 56 formed on the inner wall 21, 51 of the case 20, 50, which abutment is arranged to cooperate with one end 36, 66 of the inner wall 31, 61 of the lid 30, 60 when the lid 30, 60 is in the closed position over the opening of the case.
Claims
1. A method for attaching covers (30, 60) to openings provided in power steering cases (20, 50), The steps include inserting the lid into the opening of the case such that the O-ring seal (40), which is positioned in a first annular groove (32, 52) formed in the first inner wall (31, 51) of one of the lid and the case, is brought into contact with the frustoconical portion (24, 64) of the second inner wall (21, 61) of the other of the lid and the case, A step of applying pressure to the lid so that it is gradually compressed until it reaches the closed position of the lid on the opening of the case, where the O-ring seal (40) extends beyond the frustoconical portion (24, 64), faces the first annular groove, and tends to recover to a less deformed shape in the second annular groove (22, 62) formed in the second inner wall. Methods that include...
2. The lid (30) has the first inner wall (31) formed on it, and the case (20) has the second inner wall (21) formed on it, or The case (50) has the first inner wall (51) formed on it, and the lid (60) has the second inner wall (61) formed on it. The method according to claim 1.
3. When the lids (30, 60) are in the closed position, The peripheral rim (33, 63) of the lid abuts against the annular edge (23, 53) of the opening of the case (20, 50), and / or The first inner wall (31) of the lid (30) abuts against the frustoconical portion (24) of the case, and / or One end (36, 66) of the second inner wall (61) of the lid (30, 60) abuts against the annular shoulder formed by the first and second inner walls (21, 51) of the case. The method according to claim 1.
4. In the closed position of the lid (30, 60), the O-ring seal (40) in the first and second annular grooves (22, 32, 52, 62) maintains its elastic deformation. The method according to any one of claims 1 to 3.
5. The O-ring seal (40) has a cross-section sized to hold the lid (30, 60) in the closed position against a pressure difference of 35 kPa between the inside and outside of the case (20, 50). The method according to any one of claims 1 to 3.
6. The opening in the power steering case (20, 50) and A lid (30, 60) configured to close the aforementioned opening, The lid and case are equipped with an O-ring seal (40) positioned in a first annular groove (32, 52) formed in the first inner wall (31, 51) of one of the lids and cases, The second inner wall (21, 61) of the lid and the other side of the case has a frustoconical portion (24, 64) that faces the first annular groove and gradually compresses the O-ring seal (40) in the second annular groove (22, 62) formed in the second inner wall until the lid is closed and the O-ring seal (40) returns to its initial, less deformed shape. Power steering case (20, 50).
7. The lid (30) has the first inner wall (31) formed on it, and the case (20) has the second inner wall (21) formed on it, or The case (50) has the first inner wall (51) formed on it, and the lid (60) has the second inner wall (61) formed on it. The case described in claim 6.
8. The lid (30, 60) includes peripheral rims (33, 63) configured to abut against the edges (23, 53) of the opening of the case (20, 50) when the lid is in the closed position. The case described in claim 6.
9. The first annular groove (32, 52) is deeper than the second annular groove (22, 62), The case according to any one of claims 6 to 8.
10. The first annular grooves (32, 52) and the second annular grooves (22, 62) are molded such that 70% to 75% of the O-ring seal (40) is housed in the first annular groove, and 30% to 25% of the O-ring seal (40) is housed in the second annular groove. The case according to any one of claims 6 to 8.
11. The O-ring seal (40) has a cross-section sized to hold the lid (30, 60) in the closed position despite a pressure difference of 35 kPa between the inside and outside of the case (20, 50). The case according to any one of claims 6 to 8.
12. The frustoconical portion (24, 64) has a flare angle of 15° to 30° with respect to the insertion direction of the lid within the opening of the case (20, 50). The case according to any one of claims 6 to 8.
13. The first and second annular grooves (22, 52) formed in the case (20, 50) are offset toward the inside of the case by a distance of 0.3 mm or more and 0.8 mm or less. The case according to any one of claims 6 to 8.