Rzeppa joint with protective cover

Abstract

The protective cover (30) has an outer joint member (21) and an inner joint member (23), a shaft member (2) linked to the inner joint member (23) in a manner capable of transmitting torque, and a cylindrical protective cover (30) that seals a joint interior space, the protective cover (30) being a molded product of a flexible material that has a large-diameter cylindrical portion (31), a small-diameter cylindrical portion (32), an elastic portion (33) that extends from the small-diameter cylindrical portion (32) toward the large-diameter cylindrical portion (31) and elastically deforms in response to relative angular displacement of the two joint members, and a connecting portion (34) that connects the large-diameter cylindrical portion (31) and the elastic portion (33). The connecting portion (34) of the protective cover (30) is formed to have a thicker wall than the elastic portion (33).

Description

Technical Field

[0001] This invention relates to a constant velocity universal joint assembled in the power transmission mechanism of motor vehicles and various industrial machinery, and is a constant velocity universal joint with a protective cover equipped with a cylindrical protective cover that functions as a sealing component. Background Technology

[0002] For example, a motor vehicle equipped with a drive source such as an engine or electric motor mounted on its chassis has a power transmission device for transmitting the output of the drive source to the drive wheels. Such a power transmission device may include, for example, a drive shaft that comprises a fixed constant velocity universal joint that allows only angular displacement of the two connected shafts, a sliding constant velocity universal joint that allows both angular and axial displacement of the two connected shafts, and a shaft member in which the inner coupling members of the two aforementioned constant velocity universal joints, spaced apart in the vehicle width direction, are connected to each other in a manner capable of torque transmission. This shaft member is also referred to as an "intermediate shaft," "power transmission shaft," etc.

[0003] In the aforementioned drive shaft, a cylindrical protective cover (protective cover for constant velocity universal coupling) is provided between the shaft member and the outer coupling member of each constant velocity universal coupling, serving as a sealing component. A large-diameter cylindrical section and a small-diameter cylindrical section are respectively provided at one end of the axial direction of the protective cover. The large-diameter cylindrical section is installed on the outer coupling member, and the small-diameter cylindrical section is installed on the shaft member. This seals the internal space of the coupling defined between the outer coupling member, the shaft member, and the protective cover, preventing lubricant filled in this space from leaking to the outside and preventing foreign matter from entering the space.

[0004] Between the large-diameter cylindrical portion and the small-diameter cylindrical portion of the protective cover, there is a portion (elastic portion) that elastically deforms in response to the relative displacement of the outer coupling member and the inner coupling member (the shaft member connected to the inner coupling member). As such an elastic portion, there are elastic portions that are serpentine in shape and elastic portions that are not serpentine in shape. As an example of the latter, the elastic portion described in Patent Document 1 below is known.

[0005] The protective cover in Patent Document 1 is entirely formed of a flexible material (elastic material) such as resin or rubber. The elastic part is formed with a cross-section that is approximately J-shaped, having a valley (fold-back part) that bends into an arc shape in a free state. This elastic part is connected to the large-diameter cylindrical part via a connecting part (referred to as the "shoulder of the protective cover" in Patent Document 1). Multiple reinforcing ribs extending axially are provided at intervals in the circumferential direction at the connecting part. This improves the rigidity (strength) of the connecting part and suppresses the expansion and deformation of the elastic part due to the centrifugal force of the constant velocity universal coupling during rotation, thus ensuring stable sealing performance required by the protective cover. Furthermore, the protective cover of Patent Document 1, which is entirely made of flexible material, has the advantage of being less expensive compared to protective covers where the connecting part and the large-diameter cylindrical part are partially made of metal cylindrical (ring-shaped) components.

[0006] Prior technology literature

[0007] [Patent Documents]

[0008] Patent Document 1: Japanese Patent Application Publication No. 11-190358 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] However, constant velocity universal couplings with protective covers have the following characteristics: they are used in high-speed rotational transmission applications where a large centrifugal force is generated, causing the elastic part of the protective cover to expand and deform; and they are used in relatively low-speed rotational transmission applications where a small centrifugal force is generated, causing the elastic part of the protective cover to expand and deform. Especially in the latter case, the necessity of adopting the countermeasures adopted in Patent Document 1, which increase the complexity of the protective cover shape and increase the cost, to improve rigidity (strength) is considered small. However, during the transport and installation of constant velocity universal couplings (including the drive shaft of the constant velocity universal coupling), bending of the constant velocity universal coupling (relative angular displacement of the two coupling members) sometimes occurs accidentally due to the weight of the shaft members. At this time, if the rigidity of the protective cover is insufficient, there is a concern that the elastic part of the protective cover may be clamped (bitten) between the outer coupling member and the shaft member and damaged.

[0011] In view of the above-mentioned actual situation, the main objective of the present invention is to realize a constant velocity universal joint with a protective cover, which can effectively prevent large angular displacement of the two coupling components caused by the weight of the shaft components connected to the inner coupling components, and further prevent the elastic part of the protective cover from biting in (damaging) caused by this. It also helps to simplify, improve efficiency and durability of the conveying and transportation operations of the constant velocity universal joint with the protective cover (including the power transmission device of the constant velocity universal joint with the protective cover) and the assembly operations relative to the assembly objects such as vehicles.

[0012] [Methods used to solve problems]

[0013] The constant velocity universal coupling with a protective cover, which is a product of the present invention completed to achieve the above-mentioned objectives, comprises:

[0014] The coupling comprises an outer coupling member and an inner coupling member, which are angularly displaced relative to each other via a torque transmission member; a shaft member, which is connected to the inner coupling member in a manner capable of torque transmission; and a cylindrical protective cover that seals the internal space of the coupling defined together with the outer coupling member and the shaft member.

[0015] The protective cover is a molded product made of flexible material, consisting of a large-diameter cylindrical section, a small-diameter cylindrical section, an elastic section, and a connecting section. The large-diameter cylindrical section is mounted on the outer coupling component, the small-diameter cylindrical section is mounted on the shaft component, the elastic section extends from the small-diameter cylindrical section towards the large-diameter cylindrical section and elastically deforms in response to the relative angular displacement of the two coupling components, and the connecting section connects the large-diameter cylindrical section and the elastic section.

[0016] The connecting part is formed to have a thicker wall than the elastic part.

[0017] In the protective cover of the constant velocity universal joint (hereinafter also referred to as "constant velocity universal joint") according to the present invention, which is assembled with the above-described structure, the elastic part is kept in a non-contact state relative to the outer coupling member by controlling the wall thickness of the connecting part, which is formed to be thicker than the elastic part, to resist the moment load caused by the weight of the shaft member. Therefore, the protective cover is a simple structure that does not seek to complicate the shape, and it can limit the accidental bending (relative angular displacement of the two coupling members) of the constant velocity universal joint caused by the weight of the shaft member. Therefore, it can help to simplify and improve the transportation, transport, and installation operations relative to the vehicle body of the constant velocity universal joint including the protective cover.

[0018] Here, an example of a method (step) for determining whether "the elastic part remains in a non-contact state relative to the outer coupling member due to overcoming the moment load caused by the self-weight of the shaft member" is shown.

[0019] First, in a drive shaft formed by connecting a fixed constant velocity universal joint and a sliding constant velocity universal joint to the ends of the shaft member on one side and the other side of the axial direction, remove the sliding constant velocity universal joint and set the end of the shaft member on the other side of the axial direction to be exposed.

[0020] Next, after fixing the outer coupling component of the fixed constant velocity universal coupling equipped with the protective cover according to the present invention in a horizontal position, the shaft component is released, so that the shaft component (and the inner coupling component connected to the shaft component) tilts under its own weight.

[0021] Finally, check whether the elastic part of the protective cover is in contact with the outer coupling component. If it is not in contact, it can be determined that it is "...maintained in a non-contact state" as mentioned above.

[0022] As described above, the protective cover of the constant velocity universal joint according to the present invention requires that the connecting portion be formed with a wall thickness greater than that of the elastic portion. However, when the connecting portion is made excessively thick, it may cause various problems such as impaired deformability of the protective cover, reduced workability of the constant velocity universal joint, increased cost and weight of the constant velocity universal joint including the protective cover, and reduced formability of the protective cover (making it prone to forming defects). Therefore, the inventors have focused their research and discovered a specific structure as shown below that avoids the aforementioned problems and achieves the above-mentioned objectives.

[0023] The first refers to a connecting part consisting of an annular portion and a conical portion. The annular portion has a wall thickness of 2 mm or more and 4 mm or less, and extends radially outward from the end of the large-diameter cylindrical portion of the elastic portion. The conical portion connects the annular portion to the large-diameter cylindrical portion, and gradually expands in diameter from the annular portion side towards the large-diameter cylindrical portion side.

[0024] Furthermore, when the wall thickness x of the annular portion is set to 2 mm or more and less than 3 mm, the ratio δ1 (=y / x) of the wall thickness y of the conical portion to the wall thickness x of the annular portion satisfies the following relationship (1), and when the wall thickness x of the annular portion is set to 3 mm or more and less than 4 mm, the ratio δ1 satisfies the following relationship (2).

[0025] -0.21x+1.24 ≤ δ1 ≤ -0.67x+3.31···(1)

[0026] -0.04x+0.71 ≤ δ1 ≤ -0.33x+2.33···(2)

[0027] Alternatively, when the wall thickness x of the annular portion is set to 2 mm or more and less than 3 mm, the ratio δ1 satisfies the following relationship (3) obtained by changing a part of the above relationship (1). When the wall thickness x of the annular portion is set to 3 mm or more and less than 4 mm, the ratio δ1 satisfies the following relationship (4) obtained by changing a part of the above relationship (2).

[0028] -0.21x+1.24 ≤ δ1 ≤ (-0.21x+1.24)×1.2···(3)

[0029] -0.04x+0.71 ≤ δ1 ≤ (-0.04x+0.71)×1.2···(4)

[0030] Alternatively, when the wall thickness x of the annular portion is set to 2 mm or more and less than 3 mm, the above ratio δ1 satisfies the following relationship (5) obtained by changing a part of the above relationship (1). When the wall thickness x of the annular portion is set to 3 mm or more and less than 4 mm, the above ratio δ1 satisfies the following relationship (6) obtained by changing a part of the above relationship (2).

[0031] -0.21x+1.24 ≤ δ1 ≤ (-0.21x+1.24)×1.1···(5)

[0032] -0.04x+0.71 ≤ δ1 ≤ (-0.04x+0.71)×1.1···(6)

[0033] Furthermore, as a second structure that does not cause the aforementioned problems and can achieve the above-mentioned objectives, a structure can be described as follows: a connecting portion is formed by an annular portion and a cylindrical portion. The annular portion has a wall thickness of 2 mm or more and 4 mm or less and extends radially outward from the end of the large-diameter cylindrical portion of the elastic portion. The cylindrical portion connects the annular portion to the large-diameter cylindrical portion.

[0034] Furthermore, when the wall thickness x of the annular portion is set to 2 mm or more and less than 3 mm, the ratio δ2 (=z / x) of the wall thickness z of the cylindrical portion to the wall thickness x of the annular portion satisfies the following relationship (7). When the wall thickness x of the annular portion is set to 3 mm or more and less than 4 mm, the ratio δ2 satisfies the following relationship (8).

[0035] 0.6 ≤ δ2 ≤ -0.67x+3.31···(7)

[0036] 0.6 ≤ δ2 ≤ -0.33x+2.33···(8)

[0037] In addition, as a third structure that does not cause the aforementioned problems and can achieve the above-mentioned purpose, the following structure can be cited: a connecting part is formed by an annular part and a cylindrical part. The annular part has a wall thickness of 2 mm or more and 4 mm or less and extends radially outward from the end of the large-diameter cylindrical part of the elastic part. The cylindrical part connects the annular part to the large-diameter cylindrical part, and the ratio of the wall thickness z of the cylindrical part to the wall thickness x of the annular part, δ2 (=z / x), satisfies the following relationship (9).

[0038] 0.6 ≤ δ2 ≤ 0.6×1.2···(9)

[0039] In addition, as a fourth structure that does not cause the aforementioned problems and can achieve the above-mentioned purpose, the following structure can be cited: a connecting part is formed by an annular part and a cylindrical part. The annular part has a wall thickness of 2 mm or more and 4 mm or less and extends radially outward from the end of the large-diameter cylindrical part of the elastic part. The cylindrical part connects the annular part to the large-diameter cylindrical part, and the ratio of the wall thickness z of the cylindrical part to the wall thickness x of the annular part, δ2 (=z / x), satisfies the following relationship (9).

[0040] 0.6 ≤ δ2 ≤ 0.6×1.1···(10)

[0041] It should be noted that the above relationships (1) to (10) are judged under room temperature conditions.

[0042] The constant velocity universal coupling with a protective cover described above is used when the internal space of the coupling is filled with grease as a lubricant. In this case, it is preferable that the proportion of grease in the volume of the internal space of the coupling is 35% or more. This allows for proper lubrication of the coupling's internal space over a long period. It should be noted that the "volume of the internal space of the coupling" referred to herein refers to the volume of the space defined between the outer coupling member, the shaft member, and the protective cover by the protective cover being installed on the outer coupling member and shaft member.

[0043] [Invention Effects]

[0044] As shown above, the present invention provides a constant velocity universal joint (constant velocity universal joint with a protective cover) that, through a simple protective cover, prevents relative angular displacement of the two coupling members caused by the weight of the shaft members connected to the inner coupling members, and further prevents the elastic portion from seizing. This facilitates the simplification and efficiency of conveying and transporting the constant velocity universal joint, as well as the assembly operation relative to the assembly object, and further contributes to improved durability. Attached Figure Description

[0045] Figure 1This is a longitudinal sectional view of the drive shaft, which is a component of the constant velocity universal coupling with a protective cover according to the first embodiment of the present invention.

[0046] Figure 2 It is shown Figure 1 The diagram shows the fixed constant velocity universal joint in the state of its working angle.

[0047] Figure 3 yes Figure 1 The protective cover shown is a longitudinal sectional view in its free state.

[0048] Figure 4 It is shown that in making Figure 3 The diagram shows the scatter plot of the analytical results of the numerical analysis performed during the completion of the protective cover, and it is a scatter plot showing the analytical results for the first joint model.

[0049] Figure 5 This is a scatter plot showing the analytical results for the second joint model.

[0050] Figure 6 This is a scatter plot showing the analytical results for the third joint model.

[0051] Figure 7 This is a scatter plot showing the analytical results for the fourth joint model.

[0052] Figure 8 This is a scatter plot showing the analytical results for the fifth joint model.

[0053] Figure 9 Based on Figures 4-8 A scatter plot was created to show the relationship between the wall thickness of the annular portion of the protective cover constituting the constant velocity universal joint according to the first embodiment and the ratio δ1.

[0054] Figure 10 This is a diagram showing the analytical results of the effect of the tilt angle of the tapered portion of the protective cover on the elongation strain of the elastic portion of the protective cover.

[0055] Figure 11 This is a longitudinal sectional view of the protective cover of the constant velocity universal joint according to the second embodiment of the present invention in its free state.

[0056] Figure 12 It is shown that in making Figure 11 The diagram shows the scatter plot of the analytical results of the numerical analysis performed during the completion of the protective cover, and is a diagram showing the analytical results for the sixth joint model.

[0057] Figure 13 This is a diagram showing the analytical results for the seventh joint model.

[0058] Figure 14 This is a diagram showing the analytical results for the eighth connector model.

[0059] Figure 15 Based on Figures 12-14 The production used to demonstrate Figure 11 The diagram shows the relationship between the wall thickness of the annular portion of the protective cover and the ratio δ2. Detailed Implementation

[0060] The embodiments of the present invention will be described below with reference to the accompanying drawings.

[0061] Figure 1 The diagram shows a longitudinal sectional view of a drive shaft comprising a constant velocity universal joint with a protective cover, according to the first embodiment of the present invention. Figure 2 Show Figure 1 The fixed constant velocity universal joint shown is in the working angle state. Figure 1 The drive shaft 1 shown is mounted on the chassis of a motor vehicle along the width direction and transmits torque from a drive source such as an engine or electric motor to the wheels (especially the rear wheels). The drive shaft 1 includes a sliding constant velocity universal joint 10 mounted on the drive source side (inner side), a fixed constant velocity universal joint 20 mounted on the wheel side (outer side), and a shaft member 2 connected to the inner coupling members of the two constant velocity universal joints 10 and 20 in a manner capable of torque transmission (capable of rotating as a single unit). In the following description, "axial," "radial," and "circumferential" refer to the direction parallel to the axis O of the shaft member 2, the radial direction of the circle centered on the central axis O, and the circumferential direction, respectively.

[0062] The sliding constant velocity universal joint 10 illustrated in the figure is a so-called double-offset type, and includes: an outer coupling member 11 having a bottomed cylindrical cup-shaped portion 12 with a plurality of straight outer raceway grooves 13 formed on the cylindrical inner diameter surface of the cup-shaped portion 12; an inner coupling member 14 having a plurality of straight inner raceway grooves 15 formed on the convex spherical outer diameter surface, and one end of a shaft member 2 is splined into the shaft hole; a plurality of balls 16, which are located between pairs of raceway grooves 13, 15 and transmit torque between the two coupling members 11, 14; and a retainer 17, which retains the balls 16 circumferentially spaced apart. For this sliding constant velocity universal joint 10, other known forms of sliding constant velocity universal joints, such as three-ball pin type or cross-groove type, are sometimes used instead of the double-offset type.

[0063] The sliding constant velocity universal joint 10 is equipped with a protective cover 3 made of resin or rubber that functions as a sealing component. The protective cover 3 integrally has a large-diameter cylindrical portion 4 installed on the cup-shaped portion 12 of the outer coupling member 11, a small-diameter cylindrical portion 5 installed on the shaft member 2, and a snake belly 6, which is disposed between the two cylindrical portions 4 and 5 and elastically deforms in response to the relative angular displacement and / or axial displacement of the outer coupling member 11 and the inner coupling member 14 (the shaft member 2 connected to the inner coupling member 14).

[0064] The large-diameter cylindrical portion 4 of the protective cover 3 is installed relative to the cup-shaped portion 12 of the outer coupling member 11 by fastening its outer peripheral surface with the protective cover strap 7A, and the small-diameter cylindrical portion 5 of the protective cover 3 is installed relative to the shaft member 2 by fastening its outer peripheral surface with the protective cover strap 7B. By installing the protective cover 3 relative to the outer coupling member 11 and the shaft member 2 in the above manner, the internal space of the coupling defined between the cup-shaped portion 12 of the outer coupling member 11, the shaft member 2, and the protective cover 3 is sealed, thereby preventing the lubricant filled into the internal space of the coupling from leaking to the outside and preventing foreign matter from entering the internal space of the coupling as much as possible.

[0065] Also shown in Figure 2 The fixed constant velocity universal joint 20 is a so-called ball cage type and includes: an outer coupling member 21 having a bottomed cup-shaped opening 22 with a plurality of outer raceway grooves 23 formed on the concave spherical inner diameter surface of the opening 22; an inner coupling member 24 having a plurality of inner raceway grooves 25 formed on the convex spherical outer diameter surface and having the other end of the shaft member 2 splinedly fitted into the shaft hole; a plurality of balls (torque transmission members) 26, which are located between pairs of raceway grooves 23, 25 and transmit torque between the two coupling members 21, 24; and a retainer 27 that holds the plurality of balls 26 circumferentially spaced apart. Other forms of fixed constant velocity universal joints, such as the root-cut-free type, are sometimes used for this fixed constant velocity universal joint 20.

[0066] A cylindrical protective cover 30 is fitted to the fixed constant velocity universal joint 20. The protective cover 30 is molded from a resin material mainly composed of thermoplastic elastomer and functions as a sealing component. The protective cover 30 integrally has a large-diameter cylindrical portion 31 installed on the opening 22 of the outer coupling member 21, a small-diameter cylindrical portion 32 installed on the shaft member 2, an elastic portion 33 disposed between the two cylindrical portions 31 and 32 and elastically deformable in response to the relative angular displacement of the outer coupling member 21 and the inner coupling member 24 (the shaft member 2 connected to the inner coupling member 24), and a connecting portion 34 connecting the elastic portion 33 and the large-diameter cylindrical portion 31.

[0067] The large-diameter cylindrical portion 31 of the protective cover 30 is installed relative to the outer coupling member 21 (opening 22) by fastening its outer peripheral surface with the protective cover strap 8A, and the small-diameter cylindrical portion 32 of the protective cover 30 is installed relative to the shaft member 2 by fastening its outer peripheral surface with the protective cover strap 8B. By installing the protective cover 30 relative to the opening 22 of the outer coupling member 21 and the shaft member 2 in the above manner, the internal space of the coupling defined between the opening 22 of the outer coupling member 21, the shaft member 2, and the protective cover 30 is sealed, thereby preventing the lubricant filled into the internal space of the coupling from leaking to the outside and preventing foreign matter from entering the internal space of the coupling as much as possible.

[0068] Examples of thermoplastic elastomers used for molding the protective cover 30 include polystyrene (TPS), polyvinyl chloride (TPVC), polyurethane (TPU), polyester (TPEE), and polyamide (TPA). There are cases where only one type is used, and cases where multiple types are used in combination. The protective cover 30 can also be made of flexible materials other than the aforementioned resin materials, such as materials obtained by molding rubber. Methods for molding the protective cover 30 include injection molding, blow molding, and extrusion molding. The optimal molding method is selected based on the shape, etc. In this embodiment, injection molding is preferred for molding the protective cover 30.

[0069] It should be noted that a thermoplastic elastomer with a Shore D hardness of 35 or higher and 60 or lower according to ISO 48-4 is preferred for the protective cover 30. This is because when the Shore D hardness is below 35, the rigidity of the protective cover 30 itself is insufficient. Therefore, when the fixed constant velocity universal joint 20 is at its working angle, the elastic part 33 is prone to contact with the outer coupling member 21, and damage to the elastic part 33 may occur due to this contact. On the other hand, since the fatigue strength of the protective cover 30 itself is insufficient when the Shore D hardness is greater than 60, the possibility of early damage is high when the fixed constant velocity universal joint 20 is repeatedly rotated at its working angle.

[0070] As the lubricant used to fill the internal space of the sliding constant velocity universal joint 10 and the fixed constant velocity universal joint 20, a grease obtained by mixing a base oil with a thickener and various additives is used. It should be noted that the proportion of the lubricant (grease) in the volume of the internal space of the fixed constant velocity universal joint 20 is set to 35% or more, preferably 40% or more. There are no particular restrictions on the filling location of the grease in the internal space of the coupling, but it is preferable to fill more of the grease on the coupling side (the internal space of the protective cover 30) than on the protective cover side. Alternatively, the entire amount of grease that should be filled into the internal space of the coupling may be filled on the coupling side. This is to ensure that the contact portions of the structural components (outer coupling components, etc.) of the constant velocity universal joints 10 and 20 are properly lubricated by the grease.

[0071] As a base oil for lubricating greases, widely available lubricating oils or blends thereof can be used, such as paraffinic mineral oils, naphthenic mineral oils, ester-based synthetic oils, ether-based synthetic oils, hydrocarbon-based synthetic oils, GTL, fluorinated oils, and silicone oils. Mineral oils are generally used when cost is a concern, but synthetic oils or blends are used when durability in the main operating temperature range is a priority.

[0072] As a thickener for lubricating grease, in addition to soaps such as lithium soap, compound lithium soap, calcium soap, compound calcium soap, aluminum soap, and compound aluminum soap, urea compounds such as diurea compounds and polyurea compounds can also be used, as well as other substances.

[0073] As additives to lubricating greases, various additives can be used, such as solid lubricants like molybdenum disulfide and graphite, friction modifiers like organic molybdenum, antioxidants like amines and phenols, rust inhibitors like petroleum sulfonates, dinonylnaphthalene sulfonates, and sorbitan esters, extreme pressure agents like sulfur-based additives, anti-wear agents like organic zinc and phosphorus-based additives, metal passivators like benzotriazole and sodium nitrite, and viscosity index improvers like polymethyl methacrylate and polystyrene. One or more additives may be used as needed.

[0074] exist Figure 1 In the drive shaft 1 shown, the fixed constant velocity universal joint 20 equipped with a protective cover 30 is equivalent to the "constant velocity universal joint with protective cover" involved in this invention. The elastic portion 33 and the connecting portion 34 constituting the protective cover 30 in this constant velocity universal joint with protective cover have key features. Hereinafter, the characteristic structure used in the protective cover 30 will also be referred to... Figure 3 The protective cover 30 in its free state (the state of a single component without any stress on its parts) is shown in detail in a longitudinal sectional view.

[0075] like Figure 3As shown, the elastic portion 33 of the protective cover 30 in its free state is integrally formed with a cylindrical portion extending from the small-diameter cylindrical portion 32 toward the large-diameter cylindrical portion 31, and a cross-section approximately J-shaped with a valley portion 33a curved into an arc. The wall thickness t of the elastic portion 33 is set to be approximately constant throughout the entire area of ​​the elastic portion 33, and can be set to a value that simultaneously possesses soft deformation behavior and desired durability. Specifically, it is preferable that the wall thickness t is 2 mm or less, and the ratio of the wall thickness t to the wall thickness x of the annular portion 35 and the wall thickness y of the conical portion 36 described later falls within the range of 0.3 or more and 0.7 or less (0.3x≤t≤0.7x, and 0.3y≤t≤0.7y).

[0076] The connecting portion 34 of the protective cover 30 consists of a flange-shaped annular portion 35 extending radially outward from the end of the large-diameter cylindrical portion 31 of the elastic portion 33, and a tapered portion 36 that connects the outer diameter end of the annular portion 35 to the large-diameter cylindrical portion 31 and gradually expands in diameter from the annular portion 35 to the large-diameter cylindrical portion 31. The outer diameter surface of the tapered portion 36 is formed as a conical surface without radial concavity or convexity, and an annular protrusion 37 is provided on the inner diameter surface of the tapered portion 36, which can engage axially with the opening end face of the opening 22 of the outer coupling member 21. By providing the annular protrusion 37, the axial positioning of the large-diameter cylindrical portion 31 relative to the opening 22 of the outer coupling member 21 can be easily and accurately performed.

[0077] The tilt angle α of the tapered portion 36 relative to the axial direction (here, the angle formed by the outer diameter surface of the tapered portion 36 relative to the axial direction) is set primarily considering the rate of increase of the strain (elongation strain) generated in the tapered portion 36 when the bending moment is applied to the protective cover 30 due to the relative angular displacement of the two coupling components 21 and 24, and the size of the protective cover 30. It is preferably set to be 20° or more and 30° or less (20°≤α≤30°). The upper limit of the tilt angle α (=30°) is set based on the results of experiments (numerical analysis) confirming the effect of the tilt angle α of the tapered portion 36 on the rate of increase of the strain generated in the tapered portion 36 under the action of the bending moment.

[0078] That is, referring to the analysis results shown Figure 10 It is clear that the larger the inclination angle α of the tapered portion 36, the greater the rate of increase in strain of the tapered portion 36 when the bending moment acts on the protective cover 30 (when the constant velocity universal coupling 20 is at its working angle), especially when the inclination angle α exceeds 30°, the rate of increase in strain under the action of the bending moment becomes significant. It should be noted that... Figure 10The results shown are numerical analysis results implemented using a model of a constant velocity universal coupling 20, in which a resin protective cover 30 is installed on the opening 22 of the outer coupling member 21 with an outer diameter of φ87.5mm. The outer diameter of the large diameter cylindrical part 31 is set to φ89.5mm, the outer diameter of the small diameter cylindrical part 32 is set to φ33.7mm, the wall thickness x of the annular part 35 is set to 3mm, the wall thickness y of the tapered part 36 is set to 2mm, and the wall thickness t of the elastic part 33 is set to 1.2mm.

[0079] When supplemented Figure 10 The table shown illustrates that, for example, when the constant velocity universal coupling 20, with its protective cover 30 equipped with the tapered portion 36 and a tilt angle α = 10°, undergoes a relative angular displacement of the two coupling components 21 and 24 from a working angle of 0° to a working angle of 5°, the strain increases by 9%. Based on this, the upper limit of the tilt angle α is set to 30°. On the other hand, the smaller the tilt angle α, the more axially elongated the tapered portion 36, and even the protective cover 30 including the tapered portion 36, becomes. Based on this, the tilt angle α of the tapered portion 36 relative to the axial direction is preferably set in the range of 20° or more and 30° or less.

[0080] The connecting portion 34 (comprising the annular portion 35 and the tapered portion 36) is formed with a thicker wall than the elastic portion 33 to increase rigidity. This ensures that even if the shaft member 2 connected to the inner coupling member 24 undergoes angular displacement relative to the outer coupling member 21 due to its own weight, resulting in a moment load (bending moment) acting on the protective cover 30 and causing elastic deformation of the elastic portion 33, the elastic portion 33 can resist this moment load and maintain a non-contact state relative to the opening 22 of the outer coupling member 21 (the elastic portion 33 will not bite into the shaft member 2 and the opening 22, thus preventing damage). Here, the wall thickness x of the annular portion 35 is set to 2 mm or more.

[0081] Increasing the wall thickness x of the annular portion 35 improves the anti-locking function of the elastic portion 33 during angular displacement of the coupling. However, excessively increasing the wall thickness x may lead to various problems, such as reduced formability of the protective cover 30 (making it prone to poor forming), impaired deformability of the protective cover 30 resulting in reduced workability of the constant velocity universal coupling 20 (making it unable to smoothly perform angular displacement), and increased cost and weight of the protective cover 30 (including the constant velocity universal coupling 20 with the protective cover 30). Therefore, the wall thickness x of the annular portion 35 is set to 4 mm or less. That is, the wall thickness x of the annular portion 35 is set in the range of 2 mm or more and 4 mm or less (2 mm ≤ x ≤ 4 mm).

[0082] In addition, when the wall thickness y of the tapered portion 36 is too large, similar to the case of increasing the wall thickness x of the annular portion 35, problems arise with the formability of the protective cover 30. Therefore, the upper limit is set to 4 mm, just like the wall thickness x of the annular portion 35.

[0083] However, regarding the wall thickness x of the annular portion 35 and the wall thickness y of the conical portion 36, in order to prevent the aforementioned problems while also preventing the elastic portion 33 from biting in, the inventors discovered a relationship that satisfies the formula described later through numerical analysis as a confirmation test. The analysis steps will be explained first. It should be noted that the temperature condition during the analysis was set to room temperature.

[0084] [Step 1]

[0085] Multiple protective cover models (protective cover models) were manufactured, each having a wall thickness x of the annular portion 35 that was different within the range of 2 to 4 mm. Specifically, a first protective cover model with a wall thickness x of 2.0 mm for the annular portion 35, a second protective cover model with x of 2.5 mm, a third protective cover model with x of 3.0 mm, a fourth protective cover model with x of 3.5 mm, and a fifth protective cover model with x of 4.0 mm were manufactured. Each protective cover model had an outer diameter of φ89.5 mm for the large-diameter cylindrical portion 31 and an outer diameter of φ33.7 mm for the small-diameter cylindrical portion 32.

[0086] [Step 2]

[0087] The following was confirmed: when a specified bending moment was applied to the model (joint model) of the fixed constant velocity universal coupling 20 with the above-mentioned protective cover models at a working angle of 0°, how the relative angular displacement (working angle of the constant velocity universal coupling 20) of the shaft member 2 relative to the outer coupling member 21 changed and shifted as the ratio δ1 (=y / x) of the wall thickness y of the tapered portion 36 to the wall thickness x of the annular portion 35 changed. The bending moment applied to the joint model was set to 1740 Nmm. It should be noted that the bending moment of 1740 Nmm is significantly reduced compared to the bending moment caused by the self-weight of the shaft member 2, and is about 1 / 4 to 1 / 2 of the bending moment caused by the self-weight of the shaft member 2. This was to confirm the behavior of the protective cover 30 until the elastic portion 33 of the protective cover 30 engages. For comparison, the joint model was also given bending moments of 2000 Nmm and 3000 Nmm, but the bending moment of 3000 Nmm was smaller than the bending moment caused by the self-weight of shaft member 2.

[0088] [Step 3]

[0089] A scatter plot was created for each of the aforementioned joint models, with the horizontal axis set to the ratio δ1 and the vertical axis set to the angular displacement. The scatter plot for the joint model (first joint model) assembled with the first protective cover model is shown below. Figure 4 , Figures 5-8 Each diagram shows a scatter plot of the joint models (second joint model to fifth joint model) assembled with the second to fifth protective shield models. Figures 4-8 It can be seen that the larger the ratio δ1 (the larger the wall thickness y of the tapered part 36), the higher the angular displacement suppression effect under bending moment.

[0090] Next, based on Figures 4-8 The angular displacement patterns of each joint model were examined.

[0091] • In the first joint model, when the wall thickness y of the tapered portion 36 is varied by a ratio of 0.4 to 1.5 to δ1, the angular displacement tends to change based on a ratio of δ1:0.81, regardless of the magnitude of the bending moment applied to the model. Figure 4 ).

[0092] • In the second joint model, when the wall thickness y of the tapered portion 36 is varied by a ratio of 0.4 to 1.2 to δ1, the change in angular displacement tends to change based on a ratio of δ1:0.73, regardless of the magnitude of the bending moment applied to the model. Figure 5 ).

[0093] • In the third joint model, when the wall thickness y of the tapered portion 36 is varied by a ratio of 0.4 to 1.0 to δ1, the change in angular displacement tends to change regardless of the magnitude of the bending moment applied to the model, with a ratio of δ1:0.6 as the reference. Figure 6 ).

[0094] • In the fourth joint model, when the wall thickness y of the tapered portion 36 is varied by a ratio of 0.34 to 0.86 to δ1, the change in angular displacement tends to change regardless of the magnitude of the bending moment applied to the model, with a ratio of δ1:0.56 as the reference. Figure 7 ).

[0095] • In the fifth joint model, when the wall thickness y of the tapered portion 36 is varied by a ratio of 0.3 to 0.8 to δ1, the angular displacement tends to change regardless of the magnitude of the bending moment applied to the model, with a ratio of δ1:0.56 as the reference. Figure 8 ).

[0096] according to Figures 4-8It can be seen that for each wall thickness x of the annular portion 35, there are line graphs showing steep slopes with large changes in angular displacement and line graphs showing gentle slopes with small changes in angular displacement. Furthermore, as... Figure 9 A scatter plot was created with the wall thickness x of the annular portion 35 on the horizontal axis and the ratio δ1 on the vertical axis. For each of the first to fifth protective cover models assembled with different wall thickness x of the annular portion 35 at 0.5mm intervals, the ratio δ1 at points where the tendency of angular displacement changes was plotted. Figure 9 Therefore, it was determined that, based on the wall thickness x = 3 mm of the annular portion 35, the tendency of δ1 to change is as follows: the relationship δ1 = -0.21x + 1.24 holds true between wall thicknesses x of 2.0 mm and 3.0 mm, and the relationship δ1 = -0.04x + 0.71 holds true between wall thicknesses x of 3.0 mm and 4.0 mm. Therefore,

[0097] • When the wall thickness x is greater than or equal to 2.0 mm and less than 3.0 mm, and satisfies the relationship δ1 ≥ -0.21x + 1.24, and

[0098] • A protective cover 30 that can suppress angular displacement when bending moment is applied to constant velocity universal coupling 20 when the wall thickness x is 3.0 mm or more and 4.0 mm or less and satisfies the relationship δ1≥-0.04x+0.71.

[0099] As described above, considering formability and other factors, the wall thickness y of the tapered portion 36 is set to an upper limit of 4.0 mm (y≤4.0 mm) and is set to y=4.0.

[0100] When the wall thickness of the annular portion 35 is set to x = 2.0 mm, δ1 = (y / x) = 2.0.

[0101] When the wall thickness of the annular portion 35 is set to x = 2.5 mm, δ1 = 1.6.

[0102] When the wall thickness of the annular portion 35 is set to x = 3.0 mm, δ1 = 1.33.

[0103] When the wall thickness of the annular portion 35 is set to x = 3.5 mm, δ1 = 1.14.

[0104] • When the wall thickness of the annular portion 35 is set to x=4.0mm, δ1=1.0.

[0105] Furthermore, the value of δ1 corresponding to the aforementioned wall thickness x is plotted on... Figure 9Therefore, it was determined that, under this condition, the tendency of δ1 to change is also based on the wall thickness x=3mm of the annular portion 35. The relationship δ1=-0.67x+3.31 holds true when the wall thickness x is between 2.0mm and 3.0mm, and the relationship δ1=-0.33x+2.33 holds true when the wall thickness x is between 3.0mm and 4.0mm.

[0106] As can be seen from the above, in this embodiment, the protective cover 30 has a connecting portion 34 with a wall thickness greater than that of the elastic portion 33, and the connecting portion 34 is composed of an annular portion 35 and a conical portion 36. The annular portion 35 has a wall thickness of 2.0 mm or more and 4.0 mm or less, and the conical portion 36 connects the annular portion 35 to the large-diameter cylindrical portion 31, gradually increasing in diameter from the annular portion side to the large-diameter cylindrical portion side. In this embodiment of the protective cover 30,

[0107] When the wall thickness x of the annular portion 35 is set to be 2 mm or more and less than 3 mm, the ratio δ1 (=y / x) of the wall thickness y of the conical portion 36 to the wall thickness x of the annular portion 35 satisfies the following relationship (1).

[0108] When the wall thickness x of the annular portion is set to 3 mm or more and 4 mm or less, the above ratio δ1 satisfies the following relationship (2). If the wall thickness y of the tapered portion 36 is set in this way, it is a simple structure with excellent formability and deformability. Furthermore, it is possible to achieve a protective cover 30 at low cost that can prevent the elastic portion 33 from being bitten or damaged due to large bending of the constant velocity universal coupling 20 (large angular displacement of the shaft member 2 relative to the outer coupling member 21).

[0109] -0.21x+1.24 ≤ δ1 ≤ -0.67x+3.31···(1)

[0110] -0.04x+0.71 ≤ δ1 ≤ -0.33x+2.33···(2)

[0111] It should be noted that the wall thickness y of the tapered portion 36 can also be set in the following way: when the wall thickness x of the annular portion 35 is set to 2 mm or more and less than 3 mm, the above ratio δ1 satisfies the following relationship (3) obtained by changing a part of the above relationship (1).

[0112] When the wall thickness x of the annular portion 35 is set to 3 mm or more and 4 mm or less, the above ratio δ1 satisfies the following relationship (4) obtained by changing a part of the above relationship (2).

[0113] -0.21x+1.24 ≤ δ1 ≤ (-0.21x+1.24)×1.2···(3)

[0114] -0.04x+0.71 ≤ δ1 ≤ (-0.04x+0.71)×1.2···(4)

[0115] The conditions that satisfy the above relationships (3) and (4) are that the value of δ1 is in the range of Figure 9 Within the area that is lightly coated. Therefore, in this case, it is smaller than the upper limit of δ1, in other words, the range in which the wall thickness y of the tapered portion 36 can be set is narrow, but it is advantageous in reliably enjoying the effects obtained by the present invention as described above.

[0116] Alternatively, the wall thickness y of the tapered portion 36 can be set in such a way that, when the wall thickness x of the annular portion 35 is set to 2 mm or more and less than 3 mm, the ratio δ1 described above satisfies the following relationship (5) obtained by changing a part of the above relationship (1).

[0117] When the wall thickness x of the annular portion 35 is set to 3 mm or more and 4 mm or less, the above ratio δ1 satisfies the following relationship (6) obtained by changing a part of the above relationship (2).

[0118] -0.21x+1.24 ≤ δ1 ≤ (-0.21x+1.24)×1.1···(5)

[0119] -0.04x+0.71 ≤ δ1 ≤ (-0.04x+0.71)×1.1···(6)

[0120] In this case, the range in which the wall thickness y of the tapered portion 36 can be set is further narrowed by an amount smaller than the upper limit of δ1 compared to the above-described relationships (3) and (4), but it is advantageous in further reliably enjoying the effects obtained by the present invention as described above.

[0121] The following is based on Figure 11 The longitudinal sectional view of the free state shown is further based on Figures 12-15 To illustrate, we will describe the protective cover 40 of the constant velocity universal joint with protective cover according to the second embodiment of the present invention. This protective cover 40 is compared with reference to... Figures 1-3 The protective cover 30 described above is also fitted onto the fixed constant velocity universal joint 20 and functions as a sealing member that seals the internal space of the coupling defined between the outer coupling member 21 (the opening 22) and the shaft member 2.

[0122] Figure 11The protective cover 40 shown has an integral large-diameter cylindrical part 41 installed on the opening 22 of the outer coupling member 21, a small-diameter cylindrical part 42 installed on the shaft member 2, an elastic part 43 disposed between the two cylindrical parts 41 and 42 and elastically deformed by following the relative angular displacement of the outer coupling member 21 and the inner coupling member 24 (the shaft member 2 connected to the inner coupling member 24), and a connecting part 44 connecting the elastic part 43 and the large-diameter cylindrical part 41. They are molded from a resin material mainly composed of thermoplastic elastomer.

[0123] In its free state, the elastic portion 43 of the protective cover 40 is integrally formed with a cylindrical section extending from the small-diameter cylindrical portion 42 toward the large-diameter cylindrical portion 41, and a valley portion 43a curved into an arc shape, with a cross-section approximately J-shaped. The wall thickness t of the elastic portion 43 is set to be approximately constant throughout the entire area of ​​the elastic portion 43, and can be set to a value that simultaneously possesses soft deformation behavior and desired durability. Specifically, it is preferable that the wall thickness t is 2 mm or less, and the ratio of the wall thickness t to the wall thickness x of the annular portion 45 and the wall thickness z of the cylindrical portion 46 described later falls within the range of 0.3 or more and 0.7 or less (0.3x ≤ t ≤ 0.7x, and 0.3z ≤ t ≤ 0.7z).

[0124] The connecting portion 44 of the protective cover 40 is composed of a flange-shaped annular portion 45 extending radially outward from the end of the large-diameter cylindrical portion 41 side of the elastic portion 43, and a cylindrical portion 46 connecting the annular portion 45 (outer diameter end) to the large-diameter cylindrical portion 41. The outer diameter surface of the cylindrical portion 46 is formed as a constant cylindrical surface without radial concavity or convexity.

[0125] The connecting portion 44 (the annular portion 45 and the cylindrical portion 46 constituting the connecting portion 44) is formed to be thicker than the elastic portion 43 to increase rigidity, so that even if the shaft member 2 connected to the inner coupling member 24 undergoes angular displacement relative to the outer coupling member 21 due to its own weight, etc., and a bending moment is applied to the protective cover 40 and the elastic portion 43 is elastically deformed, it can resist the moment load and maintain the elastic portion 43 in a non-contact state relative to the opening 22 of the outer coupling member 21 (the elastic portion 43 will not bite into the shaft member 2 and the opening 22).

[0126] The wall thickness x of the annular portion 45 is set to a range of 2 mm or more and 4 mm or less for the same reason as setting the wall thickness x of the annular portion 35 of the protective cover 30 according to the first embodiment to a range of 2 mm or more and 4 mm or less. Furthermore, the wall thickness z of the cylindrical portion 46 is set to an upper limit of 4 mm for the same reason as setting the upper limit of the wall thickness y of the tapered portion 35 of the protective cover 40 according to the first embodiment to 4 mm.

[0127] However, regarding the wall thickness x of the annular portion 45 and the wall thickness z of the cylindrical portion 46, in order to prevent the aforementioned problems while also preventing the elastic portion 43 from biting in, the inventors discovered a relationship set to satisfy the formula described later through numerical analysis as a confirmation test. The analysis steps are explained below. It should be noted that the temperature condition during the analysis was set to room temperature.

[0128] [Step 1]

[0129] Multiple protective cover models (protective cover models) are manufactured, each having a wall thickness x of the annular portion 45 that varies within the aforementioned range of 2 to 4 mm. Here, a sixth protective cover model with a wall thickness x of 2.0 mm for the annular portion 45, a seventh protective cover model with x of 3.0 mm, and an eighth protective cover model with x of 4.0 mm are manufactured. Each protective cover model has an outer diameter of φ89.5 mm for the large-diameter cylindrical portion 41 and an outer diameter of φ33.7 mm for the small-diameter cylindrical portion 42.

[0130] [Step 2]

[0131] The following was confirmed: when a specified bending moment was applied to the model (joint model) of the fixed constant velocity universal coupling 20 with the aforementioned protective cover models at a working angle of 0°, how the relative angular displacement (working angle of the constant velocity universal coupling 20) of the shaft member 2 relative to the outer coupling member 21 changed and shifted as the ratio δ2 (=z / x) of the wall thickness y of the cylindrical part 46 to the wall thickness x of the annular part 45 changed. The bending moment applied to the joint model was set to 1740 Nmm.

[0132] [Step 3]

[0133] A scatter plot was created for each of the aforementioned joint models, with the horizontal axis set to the ratio δ2 and the vertical axis set to the angular displacement. The scatter plot for the joint models (sixth joint model to eighth joint model) assembled with the sixth to eighth protective shield models is shown below. Figures 12-14 Each. Based on Figures 12-14 It can be seen that the larger the ratio δ2 (the larger the wall thickness z of the cylindrical part 46), the higher the angular displacement suppression effect when the bending moment is applied.

[0134] Next, based on Figures 12-14 The angular displacement patterns of each joint model were examined.

[0135] • In the sixth joint model, when the wall thickness z of the cylindrical part 46 is varied by a ratio of 0.4 to 1.0 to δ2, the tendency of the angular displacement to change is based on a ratio of δ2:0.6. Figure 12 ).

[0136] • In the seventh joint model, when the wall thickness z of the cylindrical part 46 is varied by a ratio of 0.4 to 1.0 to δ2, the tendency of the angular displacement to change is based on a ratio of δ2:0.6. Figure 13 ).

[0137] • In the eighth joint model, when the wall thickness z of the cylindrical part 46 is varied by a ratio of 0.4 to 1.0 to δ2, the tendency of the angular displacement to change is based on a ratio of δ2:0.6. Figure 14 ).

[0138] according to Figures 12-14 It can be seen that for each wall thickness x of the annular portion 45, there are line graphs showing steep slopes with large changes in angular displacement and line graphs showing gentle slopes with small changes in angular displacement. Furthermore, as... Figure 15 A scatter plot was created with the wall thickness x of the annular portion 45 on the horizontal axis and the ratio δ2 on the vertical axis. For each of the sixth to eighth protective cover models, where the wall thickness x of the annular portion 45 is varied at 1.0 mm intervals, the ratio δ2 at points where the tendency of angular displacement changes was plotted. Figure 15 The wall thickness x of the annular portion 45 is constant at δ2=0.6 between 2.0mm and 4.0mm. Therefore, when the wall thickness x of the annular portion 45 is 2.0mm or more and 4.0mm or less, and the relationship δ2≥0.6 is satisfied (the wall thickness z of the cylindrical portion 46 is set in this way), a protective cover 40 can be achieved that improves the suppression effect of angular displacement when bending moment is applied to the constant velocity universal coupling 20.

[0139] As described above, considering factors such as formability, the wall thickness z of the cylindrical portion 46 is set to an upper limit of 4.0 mm (z≤4.0 mm) and is set to z=4.0.

[0140] When the wall thickness of the annular portion 45 is set to x = 2.0 mm, δ2 = (z / x) = 2.0.

[0141] When the wall thickness of the annular portion 45 is x=2.5mm, δ2=1.6.

[0142] When the wall thickness of the annular portion 45 is set to x = 3.0 mm, δ2 = 1.33.

[0143] When the wall thickness of the annular portion 45 is x = 3.5 mm, δ2 = 1.14.

[0144] • When the wall thickness of the annular portion 45 is set to x=4.0mm, δ2=1.0.

[0145] Furthermore, the value of δ2 corresponding to the aforementioned wall thickness x is plotted on... Figure 15Therefore, it was determined that the tendency of δ2 to change is based on the wall thickness x=3mm of the annular part 45. The relationship δ2=-0.67x+3.31 holds true when the wall thickness x is 2.0mm to 3.0mm, and the relationship δ2=-0.33x+2.33 holds true when the wall thickness x is 3.0mm to 4.0mm.

[0146] Based on the above, it can be concluded that... Figure 11 The protective cover 40 shown has a connecting portion 44 with a wall thickness greater than that of the elastic portion 43, and the connecting portion 44 is composed of an annular portion 45 and a cylindrical portion 46 with a constant diameter. The annular portion 45 has a wall thickness of 2.0 mm or more and 4.0 mm or less, and the cylindrical portion 46 connects the annular portion 45 to the large-diameter cylindrical portion 31. In this protective cover 40,

[0147] When the wall thickness x of the annular portion 45 is set to be 2 mm or more and less than 3 mm, the ratio δ2 (=z / x) of the wall thickness z of the cylindrical portion 36 to the wall thickness x of the annular portion 45 satisfies the following relationship (7).

[0148] When the wall thickness x of the annular portion 45 is set to be 3 mm or more and 4 mm or less, the above ratio δ2 satisfies the following relationship (8).

[0149] If the wall thickness z of the cylindrical part 46 is set in this way, it is a simple structure with excellent formability and deformability, and the protective cover 40 can be made at low cost to prevent the elastic part 43 from biting in due to the large bending of the constant velocity universal coupling 20 (large angular displacement of the shaft member 2 relative to the outer coupling member 21).

[0150] 0.6 ≤ δ2 ≤ -0.67x+3.31···(7)

[0151] 0.6 ≤ δ2 ≤ -0.33x+2.33···(8)

[0152] It should be noted that the wall thickness z of the cylindrical part 46 can also be set in such a way that the ratio δ2 described above satisfies the following relationship (9).

[0153] 0.6 ≤ δ2 ≤ 0.6×1.2···(9)

[0154] The condition that satisfies this relation (9) is that δ2 is in the position of Figure 15 Within the area that is lightly coated. Therefore, in this case, the upper limit of δ2 is smaller, in other words, the range within which the wall thickness z of the cylindrical portion 46 can be set is narrow, but it is advantageous in reliably enjoying the effects obtained by the present invention as described above.

[0155] Alternatively, the wall thickness z of the cylindrical portion 46 can be set in such a way that the ratio δ2 described above satisfies the following relationship (10).

[0156] 0.6 ≤ δ2 ≤ 0.6×1.1···(10)

[0157] In this case, the range in which the wall thickness z of the cylindrical portion 46 can be set is further narrowed by a smaller amount compared to the case where the upper limit of δ2 is subject to the above-described relation (9), but it is advantageous in further reliably enjoying the effects obtained by the present invention as described above.

[0158] The constant velocity universal coupling 20 of the first embodiment and the second embodiment, which are respectively equipped with protective covers 30 and 40, have been described above. However, appropriate modifications can be made to the constant velocity universal coupling 20 without departing from the spirit of the present invention.

[0159] in addition, Figure 1 The power transmission device shown is a rear wheel drive shaft, but the constant velocity universal joint 20 with protective cover involved in the embodiment of the present invention can also be assembled and used on the front wheel drive shaft and transmission shaft.

[0160]

Example 1

[0161] To demonstrate the usefulness of the present invention, a constant velocity universal coupling with a protective cover according to an embodiment having the structure of the present invention, and a constant velocity universal coupling with a protective cover according to a comparative example not having the structure of the present invention, were prepared, and durability verification tests were performed. In both the embodiments and the comparative examples, the constant velocity universal coupling used an 8-ball type ball cage type (see [reference]) as a type of fixed constant velocity universal coupling. Figure 1 and Figure 2 The protective cover used Figures 1-3 The type shown has a tapered portion 36 provided in the connecting portion 34. Furthermore, the internal space of each constant velocity universal joint is filled with grease having the following structure.

[0162] Base oil: mineral oil

[0163] Thickener: Urea compounds

[0164] • Additives: sulfur-based extreme pressure additives, molybdenum dithiocarbamate

[0165] • JIS cone penetration: No. 1, 310-340

[0166] The verification test confirmed the effect of the proportion of grease (lubricant) in the internal space of the coupling on the durability of the constant velocity universal coupling 20 with a protective cover, and the effect of the construction of the protective cover 30 on the durability of the protective cover 30 (operability of the drive shaft 1). Details are as follows.

[0167] [Durability Confirmation of Constant Velocity Universal Joints]

[0168] Constant velocity universal couplings are typically sized in stages according to torque load capacity, with internal specifications set for each size. Therefore, the following conditions are set for the opening 22 of the outer coupling member 21, which has an outer diameter of φ87.5mm.

[0169] • "High load durability test": When the constant velocity universal coupling 20 is rotated for a specified time with a load torque of 1400 N·m and a speed of 170 rpm under a working angle of 6°, check whether there is any damage to the coupling structural components (outer coupling component 21, inner coupling component 24, ball 26 and retainer 27).

[0170] • "Low load durability test": When the constant velocity universal coupling 20 is rotated for a specified time with a load torque of 350 N·m and a speed of 1300 rpm under a working angle of 6°, it is confirmed whether there is any damage to the structural components of the coupling.

[0171] [Durability of the protective cover (operability of the drive shaft) confirmed]

[0172] The test is designated as a "biting-in test." In this test, after supporting the outer coupling member 21 and shaft member 2 of the constant velocity universal coupling constituting the test object in a horizontal position, the support of the shaft member 2 is released, allowing it to fall naturally under its own weight. The test then checks whether the protective cover 30 (elastic part 33) has bitten in. This is because if the elastic part 33 bites in, the possibility of premature damage to the elastic part 33 due to repeated biting increases. Therefore, to avoid biting in the elastic part 33, the drive shaft 1 needs to be carefully operated. It should be noted that the protective cover 30 of the constant velocity universal coupling 20 assembled on the test object is injection molded from a resin material mainly composed of polyester thermoplastic elastomer (TPEE).

[0173] The test results are shown in Table 1 below. It should be noted that the test results for the "High Load Durability Test" and "Low Load Durability Test" are evaluated using three levels: "◎", "○", and "×". "◎" indicates that damage to the coupling structural components occurred more than 1.5 times the target time; "○" indicates that damage occurred after the target time (but less than 1.5 times the target time); and "×" indicates that damage occurred before the target time. Furthermore, the test results for the "Edge Test" are evaluated using two levels: "○" and "×". "○" indicates that the elastic part of the protective cover did not engage; and "×" indicates that the elastic part of the protective cover engaged.

[0174] [Table 1]

[0175]

[0176] According to the test results shown in Table 1, the constant velocity universal joints with protective covers involved in Examples 1 to 3 all possess high load durability, low load durability, and durability (rigidity) of the protective cover. In contrast, the constant velocity universal joint with protective cover involved in Comparative Example 1 does not meet the required durability of the protective cover, and the constant velocity universal joint with protective cover involved in Comparative Example 2 does not meet the required load durability. Therefore, it can be seen that controlling the wall thickness of the elastic part 33 and the connecting part 34 (annular part 35 and conical part 36) of the protective cover 30 is effective in preventing the protective cover 30 from biting in and improving the durability of the protective cover 30 (and improving the maneuverability of the drive shaft 1), and ensuring that the proportion of grease in the internal space of the coupling is a certain or higher is effective in improving the durability of the coupling.

[0177] [Explanation of Labels in the Attached Image]

[0178] 1. Drive shaft

[0179] 20 Fixed constant velocity universal joint

[0180] 21. Outer coupling components

[0181] 22 Mouth

[0182] 30 Protective Cover

[0183] 31 Large diameter barrel

[0184] 32 Small Diameter Cylindrical Section

[0185] 33 Elastic part

[0186] 34 Connecting parts

[0187] 35. Circular portion

[0188] 36. Conical section

[0189] 40 Protective shield

[0190] 41 Large diameter cylinder

[0191] 42 Small Diameter Cylindrical Section

[0192] 43 Elastic part

[0193] 44 Connecting parts

[0194] 45. Circular portion

[0195] 46. ​​Cylindrical section

[0196] t Wall thickness of the elastic part

[0197] x Wall thickness of the annular portion

[0198] y. Wall thickness of the conical section

[0199] z Wall thickness of the cylindrical section

[0200] δ1, δ2 ratio.

Claims

1. A constant velocity universal coupling with a protective cover, wherein, The constant velocity universal joint with protective cover includes: an outer coupling member and an inner coupling member, which are angularly displaced relative to each other via a torque transmission member; a shaft member connected to the inner coupling member in a torque-transmitting manner; and a cylindrical protective cover that seals the internal space of the coupling defined together with the outer coupling member and the shaft member. The protective cover is a molded product made of flexible material, integrally comprising a large-diameter cylindrical section, a small-diameter cylindrical section, an elastic section, and a connecting section. The large-diameter cylindrical section is mounted on the outer coupling component, the small-diameter cylindrical section is mounted on the shaft component, the elastic section extends from the small-diameter cylindrical section toward the large-diameter cylindrical section, and elastically deforms following the relative angular displacement between the outer coupling component and the shaft component, and the connecting section connects the large-diameter cylindrical section and the elastic section. The connecting portion is formed with a thicker wall than the elastic portion. Its features are, The connecting portion includes: an annular portion having a wall thickness of 2 mm or more and 4 mm or less, extending radially outward from the end of the elastic portion on the large-diameter cylindrical portion side; and a tapered portion connecting the annular portion to the large-diameter cylindrical portion, gradually increasing in diameter from the annular portion side towards the large-diameter cylindrical portion side. When the wall thickness x of the annular portion is 2 mm or more and less than 3 mm, the ratio δ1 (=y / x) of the wall thickness y of the conical portion to the wall thickness x of the annular portion satisfies the following relationship (1). When the wall thickness x of the annular portion is 3 mm or more and less than 4 mm, the ratio δ1 satisfies the following relationship (2). -0.21x+1.24 ≤ δ1 ≤ -0.67x+3.31···(1) -0.04x+0.71 ≤ δ1 ≤ -0.33x+2.33···(2).

2. The constant velocity universal coupling with protective cover according to claim 2, wherein, When the wall thickness x of the annular portion is 2 mm or more and less than 3 mm, the ratio δ1 satisfies the following relationship (3) obtained by changing a part of the relationship (1). When the wall thickness x of the annular portion is 3 mm or more and less than 4 mm, the ratio δ1 satisfies the following relationship (4) obtained by changing a part of the relationship (2). -0.21x+1.24 ≤ δ1 ≤ (-0.21x+1.24)×1.2···(3) -0.04x+0.71 ≤ δ1 ≤ (-0.04x+0.71)×1.2···(4).

3. The constant velocity universal coupling with protective cover according to claim 2, wherein, When the wall thickness x of the annular portion is 2 mm or more and less than 3 mm, the ratio δ1 satisfies the following relationship (5) obtained by changing a part of the relationship (1). When the wall thickness x of the annular portion is 3 mm or more and less than 4 mm, the ratio δ1 satisfies the following relationship (6) obtained by changing a part of the relationship (2). -0.21x+1.24 ≤ δ1 ≤ (-0.21x+1.24)×1.1···(5) -0.04x+0.71 ≤ δ1 ≤ (-0.04x+0.71)×1.1···(6).

4. The constant velocity universal joint with a protective cover according to any one of claims 1 to 3, wherein, The angle between the tapered portion and the axial direction is set to be more than 20° and less than 30°.

5. The constant velocity universal joint with protective cover according to claim 1, wherein, The constant velocity universal joint with protective cover includes: an outer coupling member and an inner coupling member, which are angularly displaced relative to each other via a torque transmission member; a shaft member connected to the inner coupling member in a torque-transmitting manner; and a cylindrical protective cover that seals the internal space of the coupling defined together with the outer coupling member and the shaft member. The protective cover is a molded product made of flexible material, integrally comprising a large-diameter cylindrical section, a small-diameter cylindrical section, an elastic section, and a connecting section. The large-diameter cylindrical section is mounted on the outer coupling component, the small-diameter cylindrical section is mounted on the shaft component, the elastic section extends from the small-diameter cylindrical section toward the large-diameter cylindrical section, and elastically deforms following the relative angular displacement between the outer coupling component and the shaft component, and the connecting section connects the large-diameter cylindrical section and the elastic section. The connecting portion is formed with a thicker wall than the elastic portion. in, The connecting portion includes: an annular portion having a wall thickness of 2 mm or more and 4 mm or less, extending radially outward from the end of the elastic portion on the large-diameter cylindrical portion side; and a cylindrical portion connecting the annular portion to the large-diameter cylindrical portion. When the wall thickness x of the annular portion is 2 mm or more and less than 3 mm, the ratio δ2 (=z / x) of the wall thickness z of the cylindrical portion to the wall thickness x of the annular portion satisfies the following relationship (7). When the wall thickness x of the annular portion is 3 mm or more and less than 4 mm, the ratio δ2 satisfies the following relationship (8). 0.6 ≤ δ2 ≤ -0.67x+3.31···(7) 0.6 ≤ δ2 ≤ -0.33x+2.33···(8).

6. The constant velocity universal coupling with protective cover according to claim 1, wherein, The constant velocity universal joint with protective cover includes: an outer coupling member and an inner coupling member, which are angularly displaced relative to each other via a torque transmission member; a shaft member connected to the inner coupling member in a torque-transmitting manner; and a cylindrical protective cover that seals the internal space of the coupling defined together with the outer coupling member and the shaft member. The protective cover is a molded product made of flexible material, integrally comprising a large-diameter cylindrical section, a small-diameter cylindrical section, an elastic section, and a connecting section. The large-diameter cylindrical section is mounted on the outer coupling component, the small-diameter cylindrical section is mounted on the shaft component, the elastic section extends from the small-diameter cylindrical section toward the large-diameter cylindrical section, and elastically deforms following the relative angular displacement between the outer coupling component and the shaft component, and the connecting section connects the large-diameter cylindrical section and the elastic section. The connecting portion is formed with a thicker wall than the elastic portion. in, The connecting portion includes: an annular portion having a wall thickness of 2 mm or more and 4 mm or less, extending radially outward from the end of the elastic portion on the large-diameter cylindrical portion side; and a cylindrical portion connecting the annular portion to the large-diameter cylindrical portion. The ratio of the wall thickness z of the cylindrical part to the wall thickness x of the annular part, δ2 (= z / x), satisfies the following relationship (9). 0.6 ≤ δ2 ≤ 0.6×1.2···(9).

7. A constant velocity universal coupling with a protective cover, wherein, The constant velocity universal joint with protective cover includes: an outer coupling member and an inner coupling member, which are angularly displaced relative to each other via a torque transmission member; a shaft member connected to the inner coupling member in a torque-transmitting manner; and a cylindrical protective cover that seals the internal space of the coupling defined together with the outer coupling member and the shaft member. The protective cover is a molded product made of flexible material, integrally comprising a large-diameter cylindrical section, a small-diameter cylindrical section, an elastic section, and a connecting section. The large-diameter cylindrical section is mounted on the outer coupling component, the small-diameter cylindrical section is mounted on the shaft component, the elastic section extends from the small-diameter cylindrical section toward the large-diameter cylindrical section, and elastically deforms following the relative angular displacement between the outer coupling component and the shaft component, and the connecting section connects the large-diameter cylindrical section and the elastic section. The connecting portion is formed with a thicker wall than the elastic portion. Its features are, The connecting portion includes: an annular portion having a wall thickness of 2 mm or more and 4 mm or less, extending radially outward from the end of the elastic portion on the large-diameter cylindrical portion side; and a cylindrical portion connecting the annular portion to the large-diameter cylindrical portion. The ratio of the wall thickness z of the cylindrical part to the wall thickness x of the annular part, δ2 (= z / x), satisfies the following relationship (10). 0.6 ≤ δ2 ≤ 0.6×1.1···(10).

8. The constant velocity universal coupling with protective cover according to claim 1, wherein, The internal space of the coupling is filled with grease as a lubricant. The proportion of the lubricating grease in the volume of the internal space of the coupling is set to be more than 35%.

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