Automobile wheel hub bearing unit

Abstract

The utility model discloses a kind of automobile wheel hub bearing units, including driving shaft, inner flange, outer flange and several steel balls being arranged between inner flange and outer flange, axial center hole is opened in inner flange, axial inner spline is equipped on the hole wall of axial center hole middle part, radial inner spline is opened in the end of inner flange, the end of driving shaft is coaxially fixed with connecting shaft, the side wall of this connecting shaft is opened with axial outer spline, the end surface of driving shaft is opened with radial outer spline, when assembling, connecting shaft is inserted into inner flange, axial outer spline is inlaid with axial inner spline, radial outer spline is inlaid with radial inner spline. The utility model is in the synergic cooperation of axial and radial hybrid spline, realizes load optimization distribution, reduces stress concentration and tooth surface wear, significantly improves the transmission reliability, bearing efficiency, impact resistance and NVH performance of wheel hub bearing unit.

Description

Technical Field

[0001] This utility model relates to the field of automotive wheel hub bearing technology, and more specifically to an automotive wheel hub bearing unit. Background Technology

[0002] As a key component connecting the wheel and the suspension system, the reliability, load-bearing efficiency, and durability of the drive connection structure of the wheel hub bearing unit directly affect the vehicle's performance and safety. With the increasingly stringent requirements for drive efficiency and lightweighting in electric vehicles, as well as the pursuit of NVH (noise, vibration, and harshness) performance in the whole vehicle, the traditional single drive connection method has reached its bottleneck.

[0003] Currently, the mainstream technical solutions are mainly divided into two categories: internal spline driver and end face spline driver.

[0004] The internal spline drive system transmits torque through the mating of the inner bore of the hub and the external spline of the drive shaft. Its advantages include a compact radial structure, high circumferential positioning accuracy, and uniform force transmission. However, it has significant inherent drawbacks: First, the internal spline requires extremely high machining precision, necessitating specialized broaching equipment, which is costly; second, the long shaft diameter mating leads to stress concentration at the hub neck, creating a weak point prone to fatigue fracture; third, the axial positioning accuracy of the drive shaft is critical during assembly, making alignment difficult; and fourth, radial clearance caused by spline wear after prolonged use can easily lead to abnormal noise. Furthermore, under alternating axial loads, severe stress concentration at the spline tooth roots poses a risk of tooth breakage.

[0005] The end-face spline drive scheme transmits torque through the spline engagement between the hub and the drive shaft end face. Its advantages include convenient axial installation, the ability to withstand some axial force thanks to the large bolt preload, and relatively simple machining. However, its disadvantages are equally prominent: torque transmission relies entirely on end-face contact, and the limited contact area leads to high contact stress, making it prone to tooth surface crushing or fretting wear; it is extremely sensitive to end-face machining accuracy (flatness, perpendicularity) and tooth surface contact uniformity, any deviation will result in uneven load distribution; under high-speed rotation or asymmetric impact loads, the circumferential positioning stiffness and accuracy of the end-face connection are inferior to internal splines, potentially inducing additional vibration and noise, and its resistance to lateral impact is weaker.

[0006] In summary, existing single-drive technologies all suffer from the contradiction of failing to simultaneously achieve high reliability, high load-bearing capacity, excellent assemblability, and strong impact resistance. Although there have been attempts in the industry to incorporate two spline structures, most of these are merely simple structural superpositions, failing to address system design from the perspectives of functional synergy and optimized load distribution, and thus failing to fundamentally solve the aforementioned technical problems.

[0007] To address the aforementioned issues, the existing technology includes a utility model patent with publication number CN214661572U entitled "Novel Hub Bearing and Drive Shaft Connection Structure," which discloses a method of using two sets of axial splines and radial splines to achieve combined operation of the two types of splines. However, this novel hub bearing and drive shaft connection structure uses a drive shaft connection unit installed at the end of the drive shaft, and then sets a set of splines on the drive shaft connection unit to achieve transmission between the drive shaft and the inner wheel. In this structure, the axial splines are all located at the ends of the inner wheel and the drive shaft connection unit, which leads to excessive end force on the inner wheel and drive shaft unit during transmission. Utility Model Content

[0008] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide an automotive wheel hub bearing unit that achieves graded torque transmission and optimized load distribution through the coordinated cooperation of axial splines and radial splines, thereby solving the technical problem that the existing single drive structure cannot simultaneously achieve high reliability, high load-bearing capacity, excellent assemblability and strong impact resistance.

[0009] To achieve the above objectives, this utility model provides the following technical solution: an automotive wheel hub bearing unit, comprising a drive shaft, an inner flange, an outer flange, and several steel balls disposed between the inner flange and the outer flange. An axial center hole is provided in the inner flange, and an axial internal spline is provided on the wall of the hole in the middle of the axial center hole. A radial internal spline is provided at the end of the inner flange. A connecting shaft is coaxially fixed to the end of the drive shaft. An axial external spline is provided on the side wall of the connecting shaft, and a radial external spline is provided on the end face of the drive shaft. During assembly, the connecting shaft is inserted into the inner flange, and the axial external spline engages with the axial internal spline, and the radial external spline engages with the radial internal spline.

[0010] As a further improvement of this utility model, a stud is coaxially fixed at one end of the connecting shaft facing away from the drive shaft. A fastening nut is threaded onto the stud, and the end face of the fastening nut abuts against the edge of the axial center hole, so that the fastening nut and the end face of the drive shaft cooperate to form a clamping inner flange structure.

[0011] As a further improvement of this utility model, the number of teeth of the radial external spline is greater than the number of teeth of the axial external spline, and the number of teeth of the radial internal spline is greater than the number of teeth of the axial internal spline.

[0012] As a further improvement of this utility model, the large pressure angle range of the axial internal spline and the axial external spline is 25° to 45°, and the small pressure angle range of the radial internal spline and the radial external spline is 14.5° to 20°.

[0013] As a further improvement of this utility model, the fastening nut is composed of a hexagonal nut and a disc skirt, with the end face of the disc skirt abutting against the end face of the inner flange.

[0014] This invention positions the axial spline pair at the center of the axial central hole, which, compared to the end position in existing technologies, results in more uniform and stable force transmission. It also significantly reduces the precision requirements for spline machining and the difficulty of assembly alignment, avoiding abnormal noise caused by spline clearance after long-term use. This significantly improves the load-bearing efficiency, impact resistance, NVH performance, and service durability of the wheel hub bearing unit. The addition of a clamping structure with a fastening nut further enhances the structural stability and axial positioning reliability after assembly. Optimizing the number of spline teeth and pressure angle parameters achieves precise load distribution between the two spline pairs, further strengthening the synergistic transmission effect and improving the fatigue resistance of the tooth surface. Attached Figure Description

[0015] Figure 1 This is an overall structural diagram of the automotive wheel hub bearing unit of this utility model; Figure 2 This is a diagram showing the internal structure of the automotive wheel hub bearing unit of this utility model. Figure 3 for Figure 1 Schematic diagram of the bearing section; Figure 4 for Figure 1 A schematic diagram of the drive shaft section. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the embodiments shown in the accompanying drawings.

[0017] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the automotive wheel hub bearing unit of this embodiment includes a drive shaft 4, an inner flange 1, an outer flange 2, and several steel balls 3 disposed between the inner flange 1 and the outer flange 2. An axial center hole 11 is provided in the inner flange 1, and an axial inner spline 12 is provided on the hole wall in the middle of the axial center hole 11. A radial inner spline 13 is provided at the end of the inner flange 1. A connecting shaft 41 is coaxially fixed to the end of the drive shaft 4. An axial outer spline 42 is provided on the side wall of the connecting shaft 41, and a radial outer spline 43 is provided on the end face of the drive shaft 4. During assembly, the connecting shaft 41 is inserted into the inner flange 1, the axial outer spline 42 is engaged with the axial inner spline 12, and the radial outer spline 43 is engaged with the radial inner spline 13.

[0018] When the vehicle is in motion, the torque output by the drive shaft 4 is simultaneously transmitted through the axial spline pair consisting of the axial external spline 42 and the axial internal spline 12, and the radial spline pair consisting of the radial external spline 43 and the radial internal spline 13. The axial spline pair, relying on its central position in the axial center hole 11, combined with the circumferentially uniform tooth surface fit, achieves precise circumferential positioning and stable basic torque transmission, solving the problem of insufficient circumferential positioning stiffness and easy vibration and noise caused by traditional end face splines. The radial spline pair, relying on the meshing structure of the large contact area of ​​the end face, distributes the large torque impact load and alternating axial load, effectively reducing the stress concentration at the tooth root and the risk of fatigue fracture of the hub neck of traditional axial internal splines. At the same time, the synergistic cooperation of the two sets of spline pairs reduces the machining accuracy requirements and assembly alignment difficulty of a single spline, avoiding the radial clearance noise problem caused by long-term wear, and achieving the technical effects of high load-bearing capacity, high reliability, low noise and easy assembly.

[0019] Reference Figure 1 , Figure 2 As shown, further, a stud 44 is coaxially fixed at one end of the connecting shaft 41 facing away from the drive shaft 4. A fastening nut 45 is threaded onto the stud 44. The end face of the fastening nut 45 abuts against the edge of the axial center hole 11, so that the fastening nut 45 and the end face of the drive shaft 4 cooperate to form the structure of clamping the inner flange 1.

[0020] By tightening the fastening nut 45, the end face of the drive shaft 4 can be tightly fitted with the end face of the inner flange 1, ensuring full engagement of the radial outer spline 43 and the radial inner spline 13. At the same time, it cooperates with the fastening nut 45 to form a bidirectional clamping of the inner flange 1, effectively limiting the axial movement between the inner flange 1 and the drive shaft 4, further improving the axial positioning accuracy and impact resistance of the structure, avoiding the problems of spline pair engagement disengagement and increased wear under alternating axial loads, and helping to enhance the cooperative transmission effect of the two sets of spline pairs.

[0021] Reference Figure 3 , Figure 4 As shown, further, the number of teeth of the radial external spline 43 is greater than the number of teeth of the axial external spline 42, and the number of teeth of the radial internal spline 13 is greater than the number of teeth of the axial internal spline 12.

[0022] The radial spline pair adopts a design with more teeth, which can increase the total contact area of ​​the tooth surface, reduce the contact stress per unit area, improve the load-bearing capacity of high torque impact loads, and avoid tooth surface crushing and fretting wear. The axial spline pair adopts a design with relatively fewer teeth, which can ensure the strength of a single tooth and circumferential positioning accuracy, reduce the machining difficulty, and achieve precise load distribution between the two spline pairs through the differential tooth design, further optimizing the load-bearing efficiency of the cooperative transmission.

[0023] Furthermore, the large pressure angle range of the axial internal spline 12 and the axial external spline 42 is 25° to 45°, and the small pressure angle range of the radial internal spline 13 and the radial external spline 43 is 14.5° to 20°.

[0024] The axial spline pair adopts a large pressure angle design, which can improve the bending strength of the tooth root and the axial load capacity, and reduce the risk of tooth breakage under alternating loads; the radial spline pair adopts a small pressure angle design, which can increase the tooth surface contact ratio, improve transmission smoothness and torque transmission efficiency, and reduce meshing impact noise. Through the differentiated matching of pressure angles, the functional synergy of the two spline pairs is further enhanced, taking into account both load capacity and NVH performance.

[0025] Reference Figure 1 , Figure 2 , Figure 4 As shown, the fastening nut 45 is further composed of a hexagonal nut and a disc skirt, with the end face of the disc skirt abutting against the end face of the inner flange 1.

[0026] The design of the disc skirt can increase the contact area between the fastening nut 45 and the inner flange 1, reduce the compressive stress per unit area, avoid crushing deformation of the end face of the inner flange 1 during tightening, and at the same time improve the uniformity of the preload, ensure the stability of the clamping structure, and further improve the structural reliability and service durability after assembly.

[0027] In summary, this utility model employs a hybrid spline drive structure with the coordinated operation of an axial spline pair consisting of an axial internal spline 12 and an axial external spline 42, and a radial spline pair consisting of a radial internal spline 13 and a radial external spline 43. Relying on the axial internal spline 12 located in the center of the axial central hole 11 of the inner flange 1, it achieves uniform and stable force transmission. Through the functional decomposition and load optimization of the two sets of spline pairs, it solves the industry pain point that existing single drive structures cannot simultaneously achieve high reliability, high load capacity, excellent assemblability, and strong impact resistance. Simultaneously, through the matching clamping and fastening structure composed of studs 44 and fastening nuts 45, and the optimized design of the tooth count and pressure angle differential parameters of the two sets of spline pairs, it further improves the overall transmission stability, load-bearing efficiency, impact resistance, NVH performance, and service durability of the wheel hub bearing unit composed of the inner flange 1, drive shaft 4, outer flange 2, and steel balls 3. It can be widely adapted to high-requirement vehicle applications such as electric vehicles.

[0028] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. An automotive wheel hub bearing unit, comprising a drive shaft (4), an inner flange (1), an outer flange (2), and a plurality of steel balls (3) disposed between the inner flange (1) and the outer flange (2), characterized in that: An axial center hole (11) is provided in the inner flange (1). An axial inner spline (12) is provided on the hole wall in the middle of the axial center hole (11). A radial inner spline (13) is provided at the end of the inner flange (1). A connecting shaft (41) is coaxially fixed at the end of the drive shaft (4). An axial outer spline (42) is provided on the side wall of the connecting shaft (41). A radial outer spline (43) is provided on the end face of the drive shaft (4). During assembly, the connecting shaft (41) is inserted into the inner flange (1). The axial outer spline (42) is engaged with the axial inner spline (12), and the radial outer spline (43) is engaged with the radial inner spline (13).

2. The automotive wheel hub bearing unit according to claim 1, characterized in that: One end of the connecting shaft (41) facing away from the drive shaft (4) is coaxially fixed with a stud (44), and a fastening nut (45) is threaded onto the stud (44). The end face of the fastening nut (45) abuts against the edge of the axial center hole (11), so that the fastening nut (45) and the end face of the drive shaft (4) cooperate to form a clamping inner flange (1).

3. The automotive wheel hub bearing unit according to claim 2, characterized in that: The number of teeth of the radial external spline (43) is greater than the number of teeth of the axial external spline (42), and the number of teeth of the radial internal spline (13) is greater than the number of teeth of the axial internal spline (12).

4. The automotive wheel hub bearing unit according to claim 3, characterized in that: The large pressure angle range of the axial inner spline (12) and axial outer spline (42) is 25° to 45°, and the small pressure angle range of the radial inner spline (13) and radial outer spline (43) is 14.5° to 20°.

5. The automotive wheel hub bearing unit according to claim 4, characterized in that: The fastening nut (45) is composed of a hexagonal nut and a disc skirt, with the end face of the disc skirt abutting against the end face of the inner flange (1).

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