Seal plate, outer joint member, constant velocity universal joint, and power transmission mechanism

Abstract

To improve the sealing performance of the seal plate while suppressing increases in manufacturing costs. [Solution] A seal plate 19 is press-fitted and fixed to the inner circumferential surface of an outer joint member 2 for a constant velocity universal joint, wherein the surface hardness of the outer circumferential surface of the seal plate 19 that contacts the inner circumferential surface of the outer joint member 2 is 140 Hv or more and 160 Hv or less.

Description

[[Technical Field]]

[0001] The present invention relates to a seal plate that is press-fitted to the inner circumferential surface of an outer joint member for a constant velocity universal joint, an outer joint member including the seal plate, a constant velocity universal joint, and a power transmission mechanism. [[Background Art]]

[0002] As a member constituting a power transmission system of an automobile or various industrial machines, a sliding type constant velocity universal joint that transmits rotational torque at a constant speed while allowing angular displacement and axial displacement between two shafts of a driving side and a driven side is known.

[0003] A sliding type constant velocity universal joint mainly includes an outer joint member, an inner joint member accommodated in the outer joint member, a torque transmission member that transmits torque between the outer joint member and the inner joint member, and the like.

[0004] For example, in a sliding type constant velocity universal joint used for a drive shaft of an automobile, the outer joint member is connected to a drive shaft on a differential gear device side. As one of the connection structures with the drive shaft, there is a configuration in which a spline-shaped connection hole 201 is provided at one axial end of an outer joint member 200 as shown in FIG. 4. Such a spline-shaped connection hole 201 is generally formed by broaching so as to penetrate the outer joint member 200. Therefore, in the outer joint member 200 having the connection hole 201, as shown in FIG. 4, a seal plate 190 is press-fitted into the outer joint member 200 to prevent a lubricant such as grease filled inside from leaking to the outside through the connection hole 201, and the connection hole 201 is sealed by the seal plate 190.

[0005] Furthermore, Patent Document 1 (Japanese Patent Publication No. 2009-58014) proposes a configuration in which the outer circumferential surface of the seal plate and the inner circumferential surface of the outer joint member (outer member) are tapered surfaces that widen toward the inside of the joint, as a measure to improve the sealing performance of the seal plate. In this case, a gap is created between the outer circumferential surface of the seal plate and the inner circumferential surface of the outer joint member, and even if lubricant enters this gap, the centrifugal force when the joint rotates presses the lubricant against the tapered surface of the outer joint member, causing the lubricant to be pushed back into the joint along the slope of the tapered surface. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-58014 [Overview of the project] [Problems that the invention aims to solve]

[0007] By the way, one of the factors that can reduce the sealing performance of a seal plate is damage to the seal plate during press-fitting.

[0008] Generally, outer joint members are made of medium-carbon or high-carbon steel, which has a higher hardness than the seal plate. Therefore, when the seal plate is pressed into the outer joint member, the outer surface of the seal plate comes into contact with the inner surface of the outer joint member, which can cause damage to the relatively lower hardness outer surface of the seal plate. If damage occurs to the seal plate, there is a risk that the lubricant may leak out through the damage. In addition, there is a risk that base oil separated from the lubricant may seep out through the damage.

[0009] Methods to improve sealing performance include adding an O-ring to the outer surface of the seal plate or applying liquid packing to the outer surface of the seal plate. However, these methods require additional steps such as forming a groove for mounting the O-ring or applying liquid packing to the outer surface of the seal plate, resulting in increased manufacturing costs due to the additional steps and increased number of parts. Another method involves integrally joining a sealing member to the outer surface of the seal plate by vulcanization bonding, but this method also presents the challenge of increased manufacturing costs. Furthermore, even when the outer surface of the seal plate is tapered, as described in Patent Document 1, the shape of the seal plate is changed, leading to increased costs.

[0010] Therefore, the present invention aims to improve the sealing performance of a seal plate while suppressing an increase in manufacturing costs. [Means for solving the problem]

[0011] To solve the above problems, the present invention provides a seal plate that is press-fitted and fixed to the inner circumferential surface of an outer joint member for a constant velocity universal joint, characterized in that the surface hardness of the outer circumferential surface of the seal plate that contacts the inner circumferential surface of the outer joint member is 140 Hv or more and 160 Hv or less.

[0012] In this way, by setting the surface hardness of the outer surface of the seal plate to 140 Hv or more and 160 Hv or less, the difference in hardness between the inner surface of the outer joint member and the outer surface of the seal plate can be reduced compared to conventional seal plates. This suppresses damage to the outer surface of the seal plate caused by contact between the outer surface of the seal plate and the inner surface of the outer joint member during press-fitting, thereby improving the sealing performance of the seal plate. Furthermore, in this invention, the sealing performance can be improved simply by changing the material of the seal plate to a material with higher hardness, eliminating the need to add parts or manufacturing processes, and thus reducing manufacturing costs. Therefore, according to this invention, it is possible to improve the sealing performance of the seal plate while suppressing an increase in manufacturing costs.

[0013] The difference in hardness between the inner surface of the outer joint member and the outer surface of the seal plate is preferably 130 Hv or more and 200 Hv or less.

[0014] In this way, by setting the hardness difference between the inner surface of the outer joint member and the outer surface of the seal plate to between 130 Hv and 200 Hv, it becomes possible to effectively suppress damage to the outer surface of the seal plate.

[0015] Furthermore, it is more preferable that the hardness difference between the inner surface of the outer joint member and the outer surface of the seal plate be between 130 Hv and 170 Hv.

[0016] By setting the hardness difference between the inner surface of the outer joint member and the outer surface of the seal plate to between 130 Hv and 170 Hv, the outer surface of the seal plate becomes even more resistant to damage, thus allowing for further improvement in sealing performance.

[0017] Furthermore, it is preferable that the seal plate according to the present invention is made of a press-molded product having a hardened treatment layer on its surface.

[0018] Because the seal plate has a hardened layer on its surface, the hardened layer can penetrate into the minute gap between the outer joint member and the seal plate during press-fitting, filling that gap. This further improves the sealing performance and more reliably suppresses the leakage of lubricant from the outer joint member.

[0019] Furthermore, the seal plate according to the present invention may have a base material which is a press-formed product of cold-rolled steel and a hardened treatment layer formed on the surface of the base material.

[0020] Furthermore, by using an outer joint member for a constant velocity universal joint in which the seal plate according to the present invention is press-fitted onto the inner circumferential surface, the leakage of lubricant from the outer joint member to the outside can be suppressed, thereby improving reliability.

[0021] Further, the seal plate according to the present invention may be applied to a constant velocity universal joint including an outer joint member, an inner joint member disposed inside the outer joint member, and a torque transmission member that transmits torque between the outer joint member and the inner joint member. In this case also, leakage of lubricant from the outer joint member to the outside can be suppressed, so reliability is improved.

[0022] Furthermore, the seal plate according to the present invention may be applied to a power transmission mechanism including a constant velocity universal joint and a shaft connected to an inner joint member of the constant velocity universal joint. In this case also, leakage of lubricant from the outer joint member to the outside can be suppressed, and reliability is improved. Effects of the Invention

[0023] According to the present invention, it becomes possible to improve the sealing performance of a seal plate while suppressing an increase in manufacturing cost. Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a schematic configuration diagram of a drive shaft according to an embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal sectional view of a sliding type constant velocity universal joint included in the drive shaft according to the embodiment of the present invention. [Figure 3] FIG. 3 is a transverse sectional view of the sliding type constant velocity universal joint according to the embodiment of the present invention. [Figure 4] FIG. 4 is a longitudinal sectional view of an outer joint member having a connection hole provided at one axial end thereof. Mode for Carrying Out the Invention

[0025] Hereinafter, an embodiment of the present invention will be described with a drive shaft, which is an example of a power transmission mechanism mounted on an automobile, taken as an example. In each drawing for explaining the embodiment of the present invention, components such as members and constituent parts having the same function or shape are denoted by the same reference numerals as far as they can be discriminated, and the description thereof will be omitted after being explained once.

[0026] Figure 1 is a schematic diagram of a drive shaft according to an embodiment of the present invention.

[0027] In the automobile 100 shown in Figure 1, a pair of drive shafts 90 are installed as a power transmission mechanism that transmits the rotational torque of the engine E, which is the drive source, to the left and right front wheels (wheels W), which are the drive wheels. The pair of drive shafts 90 mainly consist of a shaft 8 as a power transmission shaft, a fixed constant velocity universal joint 30 attached to the outboard end (outside in the vehicle width direction or wheel side) of the shaft 8, and a sliding constant velocity universal joint 1 attached to the inboard end (inside in the vehicle width direction or differential side) of the shaft 8. The rotational torque of the engine E is shifted by the transmission T, then distributed to the left and right drive shafts 90 by the differential D and transmitted to each wheel W.

[0028] Figure 2 is a longitudinal cross-sectional view of a sliding constant velocity universal joint provided in a drive shaft according to an embodiment of the present invention, and Figure 3 is a transverse cross-sectional view of the same sliding constant velocity universal joint.

[0029] The sliding constant velocity universal joint 1 shown in Figures 2 and 3 is a so-called tripod-type constant velocity universal joint, and its main components include an outer joint member 2, a tripod member 3, a roller 4, a boot 15 (see Figure 2), and a seal plate 19 (see Figure 2).

[0030] In the following explanation, "axial direction" refers to the direction X of the central axis O of the outer joint member 2 or any axis parallel thereto (see Figure 2), and "circumferential direction" refers to the circumferential direction of a circle centered on the central axis O of the outer joint member 2. Furthermore, the direction intersecting the axial direction (including perpendicular directions) will be referred to as the "radial direction."

[0031] As shown in Figure 2, the outer joint member 2 is integrally molded coaxially with a large-diameter cylindrical portion 20 and a small-diameter cylindrical portion 21 which has a smaller diameter than the large-diameter cylindrical portion 20. A connecting hole 22 is provided on the inner diameter side of the small-diameter cylindrical portion 21 into which the drive shaft of the mating member, the differential, is inserted. The connecting hole 22 is usually formed by broaching, so it is formed to penetrate the small-diameter cylindrical portion 21 in the axial direction. Therefore, the internal spaces of the small-diameter cylindrical portion 21 and the large-diameter cylindrical portion 20 are in communication through the connecting hole 22. In addition, a female spline is provided on the inner circumferential surface of the connecting hole 22, which engages with the male spline provided on the outer circumferential surface of the drive shaft. As a result, when the drive shaft is inserted into the connecting hole 22 and the male spline of the drive shaft engages with the female spline of the connecting hole 22, the drive shaft and the outer joint member 2 are integrally connected so as to be rotatable.

[0032] As shown in Figure 3, three track grooves 5 for housing the rollers 4 are provided at equal intervals along the circumferential direction on the inner circumferential surface of the large-diameter cylindrical portion 20 of the outer joint member 2. Each track groove 5 has a pair of roller guide surfaces 5a that guide the rollers 4. Furthermore, each track groove 5 and each roller guide surface 5a are formed to extend in the axial direction of the large-diameter cylindrical portion 20, and the rollers 4 are configured to reciprocate in the axial direction along the roller guide surfaces 5a.

[0033] Furthermore, a tripod member 3, which serves as an inner joint member, is housed on the inner diameter side of the large-diameter cylindrical portion 20 of the outer joint member 2. The tripod member 3 has a boss portion 6 and three leg shafts 7 (see Figure 3) that protrude radially from the boss portion 6. A female spline is formed in the central hole 6a of the boss portion 6, which engages with a male spline formed on the end of the shaft 8. Therefore, when the end of the shaft 8 is inserted into the central hole 6a and the male spline 8b and the female spline 6b engage, the shaft 8 and the tripod member 3 are connected integrally so as to be rotatable. In addition, a retaining ring 9 (see Figure 2) is attached to the end of the shaft 8 that protrudes from the central hole 6a, preventing the shaft 8 from falling out of the central hole 6a.

[0034] Each leg shaft 7 of the tripod member 3 is fitted with a roller unit 14 including a roller 4. Specifically, the roller unit 14 has a roller 4 as an outer ring, an inner ring 10 positioned inside the roller 4 and fitted onto the leg shaft 7, and a number of needle-shaped rollers 11 interposed between the roller 4 and the inner ring 10. The roller 4, the inner ring 10, and the needle-shaped rollers 11 are assembled together by washers 12 and 13 so as not to separate from each other.

[0035] As the roller 4 moves axially along the roller guide surface 5a of the track groove 5, the tripod member 3 also moves axially, thus allowing axial displacement of the tripod member 3 relative to the outer joint member 2. Furthermore, since the roller 4 is configured to be tiltable with respect to the axis of the leg shaft 7, angular displacement of the tripod member 3 relative to the outer joint member 2 is also allowed. In addition, the roller 4 also functions as a torque transmission member that transmits the rotational torque of the outer joint member 2 to the tripod member 3 when the outer joint member 2 rotates. As a result, the rotational torque of the engine E shown in Figure 1 is transmitted to the left and right wheels W via the pair of drive shafts 90.

[0036] The boot 15 is a cylindrical member made of an elastic material such as rubber or resin, and is attached to the outer circumferential surface of the outer joint member 2. Specifically, the boot 15 is attached to the outer circumferential surface of the large-diameter cylindrical portion 20 by a boot band 16 so as to cover the opening of the large-diameter cylindrical portion 20 on the side opposite to the small-diameter cylindrical portion 21 of the outer joint member 2. This seals the opening of the large-diameter cylindrical portion 20 on the side opposite to the small-diameter cylindrical portion 21.

[0037] The seal plate 19 is a lid-shaped member constructed by press-forming sheet metal, and is installed to seal the opening of the large-diameter cylindrical portion 20 that is covered by the boot 15, on the opposite side of the opening. More specifically, the seal plate 19 is press-fitted into the inner circumferential surface of the small-diameter cylindrical portion 21 on the side facing the large-diameter cylindrical portion 20 and fixed in place. In this case, the seal plate 19 has a disc-shaped sealing portion 31 that seals the opening of the small-diameter cylindrical portion 21, and a cylindrical press-fit portion 32 that protrudes axially from the periphery of the sealing portion 31. The seal plate 19 is fixed inside the outer joint member 2 by press-fitting the outer circumferential surface of the press-fit portion 32 into the inner circumferential surface of the small-diameter cylindrical portion 21.

[0038] In this way, the boots 15 and the seal plates 19 seal the openings at both ends of the outer joint member 2, thereby preventing foreign matter from entering the outer joint member 2 and preventing the leakage of lubricants such as grease that are filled inside the outer joint member 2.

[0039] In a configuration where a seal plate is press-fitted into the outer joint member, such as the sliding constant velocity universal joint according to the embodiment of the present invention, if the outer surface of the seal plate is damaged during press-fitting, there is a problem that lubricant may leak to the outside through the damage or the base oil of the lubricant may seep out.

[0040] Generally, seal plates are often constructed by press-forming cold-rolled steel sheets such as SPCC, from the standpoint of formability and manufacturing cost. On the other hand, outer joint members are generally made of medium-carbon or high-carbon steel, which has a higher hardness than seal plates. Therefore, when pressing a seal plate into an outer joint member, if the seal plate is pressed in at an angle or if the pressing of the seal plate is repeated several times, the outer surface of the seal plate may be damaged due to contact with the outer joint member. When such damage occurs, the sealing performance between the outer joint member and the seal plate decreases, and there is a risk that lubricant or base oil may leak to the outside. In addition, methods to improve the sealing performance of the seal plate include adding O-rings, applying liquid packing, and vulcanizing and bonding the sealing material, but all of these methods have the drawback of increasing manufacturing costs.

[0041] Therefore, in order to improve the sealing performance of the seal plate while suppressing an increase in manufacturing costs, the present invention proposes the following seal plate. The configuration of the seal plate will be described below using an embodiment of the present invention as an example.

[0042] In embodiments of the present invention, the seal plate is made of a material with a higher surface hardness than conventional cold-rolled steel sheets (such as SPCC). This makes the surface hardness of the seal plate 19 approximately 150 Hv. Here, for convenience, it is explained as "approximately 150 Hv," but "approximately 150 Hv" means that the surface hardness is between 140 Hv and 160 Hv. The same meaning applies in the following explanation. Furthermore, the surface hardness (Hv) in the explanation of the present invention refers to the hardness measured using a Vickers hardness tester as specified in the JIS standard (JIS Z 2244:2009). Examples of materials with a surface hardness of approximately 150 Hv include austenitic stainless steel.

[0043] Since the surface hardness of SPCC, which is commonly used as a material for seal plates, is approximately 110 Hv, increasing the surface hardness of the seal plate to 150 Hv can increase its surface hardness by approximately 40 Hv compared to an SPCC seal plate. This reduces the difference in hardness between the inner surface of the outer joint member and the outer surface of the seal plate.

[0044] For example, if S35C carbon steel specified in JIS standards is used as the material for the outer joint member, its surface hardness will be approximately 280 Hv to 350 Hv due to the effect of work hardening caused by cold forging. On the other hand, conventional seal plates made of SPCC have a surface hardness of about 110 Hv, so the hardness difference between it and the inner surface of the outer joint member will be approximately 170 Hv to 240 Hv. In contrast, the seal plate according to the embodiment of the present invention has a surface hardness of about 150 Hv (140 Hv to 160 Hv), so the hardness difference between it and the inner surface of the outer joint member made of the same S35C will be approximately 130 Hv to 200 Hv, thus reducing the hardness difference. In other words, by setting the surface hardness of the seal plate to 150 Hv, the difference in hardness between the outer circumferential surface of the press-fit portion 32 of the seal plate 19 shown in Figure 2 and the inner circumferential surface of the portion of the outer joint member 2 into which the press-fit portion 32 is press-fitted can be made between 130 Hv and 200 Hv.

[0045] In the case of the outer joint member, the areas on the inner circumferential surface where the track grooves and the female splines of the connecting holes are provided are usually heat-hardened by high-frequency induction hardening, in addition to the outer circumferential surface. However, the inner circumferential surface where the seal plate is press-fitted is not heat-hardened. Therefore, the difference in hardness between the inner circumferential surface of the outer joint member and the outer circumferential surface of the seal plate usually refers to the difference between the hardness of the inner circumferential surface of the unheat-hardened portion of the outer joint member and the hardness of the outer circumferential surface of the seal plate that is press-fitted into that inner circumferential surface.

[0046] As described above, in the embodiments of the present invention, by setting the surface hardness of the outer circumferential surface of the seal plate to approximately 150 Hv, that is, between 140 Hv and 160 Hv, the hardness difference between the inner circumferential surface of the outer joint member and the outer circumferential surface of the seal plate can be reduced. This makes it possible to suppress damage to the outer circumferential surface of the seal plate caused by contact between the outer circumferential surface of the seal plate and the inner circumferential surface of the outer joint member during press-fitting. For example, as described above, by setting the hardness difference between the inner circumferential surface of the outer joint member and the outer circumferential surface of the seal plate to between 130 Hv and 200 Hv, damage to the outer circumferential surface of the seal plate can be effectively suppressed.

[0047] Thus, according to the present invention, the occurrence of scratches on the outer surface of the seal plate can be suppressed, thereby improving sealing performance and highly suppressing the leakage of lubricant from the outer joint member to the outside. As a result, the reliability of the outer joint member equipped with the seal plate, the constant velocity universal joint, and the power transmission mechanism is improved.

[0048] Furthermore, in this invention, sealing performance can be improved simply by changing the material of the seal plate to a material with higher hardness, without adding any parts or manufacturing processes. Therefore, according to this invention, manufacturing costs can be reduced compared to methods that improve sealing performance by adding O-rings, applying liquid packing, or vulcanizing and bonding the sealing material. Accordingly, according to this invention, it is possible to improve the sealing performance of the seal plate while suppressing an increase in manufacturing costs.

[0049] In the above embodiment, an example is given where the hardness difference between the inner surface of the outer joint member and the outer surface of the seal plate is 130 Hv or more and 200 Hv or less. However, it is more preferable that the hardness difference be 130 Hv or more and 170 Hv or less. By setting the hardness difference to 130 Hv or more and 170 Hv or less, the outer surface of the seal plate becomes even more resistant to damage, and further improvement in sealing performance can be expected.

[0050] Furthermore, the seal plate is preferably a press-formed product from the viewpoint of formability and manufacturing cost, and more preferably has a hardened layer on its surface that has been subjected to a hard surface treatment such as hard plating. For example, the seal plate may have a base material that is a press-formed product of cold-rolled steel and a hardened layer formed on the surface of the base material.

[0051] If the seal plate has a hardened layer on its surface, the hardened layer of the seal plate can fill the minute gap between the outer joint member and the seal plate during press-fitting. Generally, the inner circumferential surface of the outer joint member is formed by machining, so lead marks (fine cutting grooves) formed during machining are present on the inner circumferential surface. Therefore, when the seal plate is press-fitted into the inner circumferential surface of the outer joint member, these lead marks may become gaps between the outer joint member and the seal plate, potentially causing lubricant leakage. However, if the seal plate has a hardened layer on its surface, the hardened layer of the seal plate can fill the minute gap between the outer joint member and the seal plate during press-fitting by filling the lead marks, thereby improving the sealing performance. This makes it possible to more reliably suppress lubricant leakage from the outer joint member. The hardened layer of the seal plate may be formed in advance on the base material before press-forming, or it may be formed on the surface of the base material (press-formed product) after press-forming.

[0052] Examples of hard surface treatment methods for forming a hardened layer on a seal plate include zinc plating, nickel plating, and zinc-based alloy plating.

[0053] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention.

[0054] In the embodiments described above, the present invention was explained using a drive shaft mounted on an automobile as an example. However, the present invention is applicable not only to drive shafts, which are an example of a power transmission mechanism, but also to power transmission mechanisms used in various other industrial machines.

[0055] Furthermore, the sliding constant velocity universal joint equipped with the seal plate according to the present invention is not limited to a tripod-type constant velocity universal joint as shown in Figures 2 and 3, but may also be a double-offset type constant velocity universal joint (DOJ) such as Patent Document 1, which is equipped with a ball as a torque transmission member. [Explanation of Symbols]

[0056] 1. Sliding type constant velocity universal joint 2. Outer joint member 3. Tripod members (internal joint members) 4. Rollers (torque transmission members) 8 shafts 19 Seal Plate 90 Drive shaft (power transmission mechanism)

Claims

1. A seal plate that is press-fitted and fixed to the inner circumferential surface of an outer joint member for a constant velocity universal joint, A seal plate characterized in that the surface hardness of the outer surface of the seal plate that contacts the inner surface of the outer joint member is 140 Hv or more and 160 Hv or less.

2. The seal plate according to claim 1, wherein the difference in hardness between the inner circumferential surface of the outer joint member and the outer circumferential surface of the seal plate is 130 Hv or more and 200 Hv or less.

3. The seal plate according to claim 1, wherein the difference in hardness between the inner circumferential surface of the outer joint member and the outer circumferential surface of the seal plate is 130 Hv or more and 170 Hv or less.

4. The seal plate according to claim 1, comprising a press-molded product having a hardened treatment layer on its surface.

5. A seal plate according to claim 1, comprising a base material which is a press-formed product of cold-rolled steel, and a hardened treatment layer formed on the surface of the base material.

6. An outer joint member for a constant velocity universal joint, characterized in that the seal plate described in claim 1 is press-fitted into the inner circumferential surface.

7. A constant velocity universal joint comprising an outer joint member as described in claim 6, an inner joint member disposed inside the outer joint member, and a torque transmission member that transmits torque between the outer joint member and the inner joint member.

8. A power transmission mechanism comprising a constant velocity universal joint as described in claim 7, and a shaft connected to the inner joint member of the constant velocity universal joint.

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