Reinforced structure universal joint cross

Abstract

The present application relates to the technical fields of automobile chassis drive shaft universal joint, in particular to a reinforced structure universal joint cross shaft. The reinforced structure universal joint cross shaft comprises a shaft body, a shaft head and a reinforcing rib. Four shaft heads are distributed along the circumference of the shaft body; the projection of the four shaft heads along the axis of the shaft body is in the shape of a cross; the shaft head comprises a shaft neck, a first convex ring and a second convex ring; multiple reinforcing ribs are arranged between adjacent shaft heads; the length direction of the reinforcing rib is arranged around the axis of the shaft body; the surface of the reinforcing rib comprises a first curved surface; the reference cross section passes through the axis of the shaft body; the reference cross section passes through part of the reinforcing rib; in the reference cross section, the connecting line between the midpoint of the cross section line of the first curved surface and the geometric center point is the reference line; the included angle between the reference line and the axis of the shaft body is an acute angle. In this way, the problem of improving the overall strength of the cross shaft while ensuring lightweight and equal strength design of the cross shaft is solved.

Description

Technical Field

[0001] This invention relates to the field of universal joint technology for automotive chassis drive shafts, and more specifically, to a reinforced universal joint cross shaft. Background Technology

[0002] Universal joints are one of the key transmission components in automobiles, and their performance directly affects the vehicle's power transmission efficiency, driving stability, and handling safety. In automotive powertrain systems, universal joints are mainly used to connect drive shafts with different axes, enabling power transmission at varying angles. For example, between the engine and drive axle, due to factors such as frame deformation and suspension movement, the relative positions of the input and output shafts constantly change. Through its structural characteristics, the universal joint can stably transmit torque even when the two shafts are at an angle, ensuring smooth power delivery from the engine to the wheels. A cross-shaft universal joint is a type of universal joint that includes a cross-shaft, rolling elements, seals, and end caps. The cross-shaft typically consists of a shaft body and four shaft ends extending outwards in four directions from the shaft body. The structural design of the cross-shaft tends to be of equal strength. Each shaft end includes a journal, a first cam ring, and a second cam ring. However, the different manufacturing processes of various parts of the universal joint cross shaft result in variations. For example, the shaft body is typically forged, the first convex ring near the shaft body is usually machined, and the second convex ring and journal near the journal are precision ground. This leads to differences in the precision of the actual quality control of the universal joint cross shaft. In static torsional strength destructive tests, the fracture sites of the universal joint cross shaft vary, with fracture failures possible at the journal, the gap between adjacent shaft ends on the shaft body, and the first and second convex rings. The design of universal joint cross shafts is currently trending towards lightweight construction. Therefore, given the different manufacturing processes of various parts of the universal joint cross shaft, how to improve the overall strength of the cross shaft while ensuring its lightweight design and achieving a near-equal strength design has become a pressing technical problem. Summary of the Invention

[0003] To address the challenge of improving the overall strength of the universal joint cross shaft while ensuring its lightweight design and near-equal strength, this invention provides a reinforced structural universal joint cross shaft, comprising:

[0004] The shaft body has its geometric center at the midpoint of its own axial direction; the surface of the shaft body is a forged blank surface.

[0005] The shaft head comprises four shaft heads distributed circumferentially along the shaft body; the axis of each shaft head is perpendicular to the axis of the shaft body; the projection of the four shaft heads along the axial direction of the shaft body forms a cross shape; the shaft head is integrally formed with the shaft body; each shaft head includes a journal, a first convex ring, and a second convex ring; the journal, the first convex ring, and the second convex ring are coaxially arranged; the diameter of the journal is smaller than the diameter of the first convex ring; the diameter of the first convex ring is smaller than the diameter of the second convex ring; the first convex ring and the second convex ring are located at the end of the journal near the shaft body; the second convex ring is located on the side of the first convex ring near the shaft body; the surfaces of the journal and the first convex ring are both ground and finished surfaces; the surface of the second convex ring is machined surface.

[0006] A plurality of reinforcing ribs are provided; the plurality of reinforcing ribs are distributed between adjacent shaft ends; the length direction of the reinforcing ribs is arranged around the axis of the shaft body; the surface of the reinforcing ribs includes a first curved surface; a reference section passes through the axis of the shaft body; the reference section passes through a portion of the reinforcing ribs; in the reference section, the line connecting the midpoint of the cross-section line of the first curved surface to the geometric center point is a reference line; the angle between the reference line and the axis of the shaft body is an acute angle.

[0007] In some embodiments, the axis of the shaft body is perpendicular to the central plane, and the geometric center point is located in the central plane; in the reference section, the center of the cross-section line of the first surface is located on the side of the reference line closer to the central plane.

[0008] In some embodiments, the angle between the reference line and the central plane is between 24° and 30°.

[0009] In some embodiments, the surface of the reinforcing rib further includes a first plane and a second plane; the first curved surface is located between the first plane and the second plane; the first plane is located on the side of the first curved surface away from the central plane; in the reference cross-section, the length of the cross-sectional line of the first plane is less than the length of the cross-sectional line of the second plane.

[0010] In some embodiments, the surface of the reinforcing rib further includes two transition surfaces; one of the transition surfaces is located between the first plane and the surface of the shaft body, and the other transition surface is located between the second plane and the surface of the shaft body.

[0011] In some embodiments, the angle between the first plane and the central plane is between 4° and 10°.

[0012] In some embodiments, the angle between the second plane and the axis of the shaft body is between 11° and 17°.

[0013] In some embodiments, the height of the reinforcing rib protruding from the surface of the shaft body is 1mm to 2mm.

[0014] In some embodiments, four reinforcing ribs are grouped together; each group of reinforcing ribs is concentrically arranged; and two groups of reinforcing ribs are arrayed along the axial direction of the shaft body.

[0015] In some embodiments, the reinforced universal joint cross shaft further includes bearings; four bearings are provided; each bearing is provided in a one-to-one correspondence with the shaft head; and each bearing is sleeved on the journal.

[0016] To address the challenge of improving the overall strength of the cross shaft while ensuring its lightweight design and near-equal strength, this invention offers the following advantages:

[0017] By incorporating multiple reinforcing ribs between adjacent shaft ends, the weak area of ​​stress concentration at the connection between the shaft end and the shaft body can be precisely reinforced, reducing localized high stress caused by abrupt changes in root force when the shaft end is subjected to load. Simultaneously, the reinforcing ribs are positioned along the shaft body axis, forming a uniformly distributed annular reinforcement structure. This allows the torque and stress on the cross bearing to be evenly transferred to the shaft body, preventing excessive local structural loads. Furthermore, the first curved surface of the reinforcing rib forms an acute angle between the reference line and the shaft body axis in the reference section, resulting in a longer reinforcing rib length on the shaft body, rather than the shortest length at the exact midpoint between adjacent shaft ends. Under combined stress scenarios, this distributes stress along the inclined direction over a wider area of ​​the shaft body, preventing stress concentration caused by sudden changes in structural dimensions. Combined with the synergistic effect of multiple reinforcing ribs providing "multi-point support," the overall stiffness of the connection between the shaft body and the shaft end is significantly improved, thereby enhancing the overall strength and service life of the cross bearing. Attached Figure Description

[0018] Figure 1 A schematic diagram of a reinforced universal joint cross shaft structure according to one embodiment is shown;

[0019] Figure 2 It shows Figure 1 A cross-sectional view along line AA of the reinforced universal joint cross shaft in the middle;

[0020] Figure 3 It shows Figure 2 A schematic diagram of the structure of the cross-sectional area in the diagram;

[0021] Figure 4 It shows Figure 2 A magnified view of section B in the diagram;

[0022] Figure 5 A schematic diagram of a reinforced universal joint cross shaft structure according to another embodiment is shown.

[0023] Reference numerals: 10 Shaft body; 20 Shaft head; 21 Shaft journal; 22 First convex ring; 23 Second convex ring; 30 Reinforcing rib; 31 First curved surface; 32 First plane; 33 Second plane; 34 Transition curved surface; 40 Reference line; 50 Center plane; 60 Bearing. Detailed Implementation

[0024] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, and are not intended to imply any limitation on the scope of the disclosure.

[0025] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments and are not intended to limit the indicated devices, elements, or components to having a specific orientation or being constructed and operated in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientations or positional relationships; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances. In addition, the terms "installed", "set up", "equipped with", "connected", and "linked" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, the terms "first," "second," etc., are mainly used to distinguish different devices, elements, or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0026] Example 1:

[0027] Universal joints are one of the key transmission components in automobiles, and their performance directly affects the vehicle's power transmission efficiency, driving stability, and handling safety. A cross-shaft universal joint is a type of universal joint that includes a cross-shaft, rolling elements, seals, and end caps. A cross-shaft typically includes a shaft body 10 and four shaft ends 20 extending outwards in four directions from the shaft body 10. Current cross-shaft structural designs tend towards equal strength and lightweight construction. To address the issue of improving the overall strength of the cross-shaft while ensuring lightweight construction and achieving equal strength design, this embodiment discloses a reinforced universal joint cross-shaft.

[0028] In this embodiment, as Figure 1 As shown, the reinforced universal joint cross shaft consists of a shaft body 10, a shaft head 20, and a reinforcing rib 30.

[0029] The shaft body 10 has its geometric center at its midpoint along its axial direction. The surface of the shaft body 10 is a forged blank surface, reducing processing costs while ensuring the strength of the shaft body 10. Four shaft heads 20 are distributed circumferentially along the shaft body 10. The axes of the shaft heads 20 are perpendicular to the axis of the shaft body 10, and the projections of the four shaft heads 20 along the axial direction of the shaft body 10 form a cross shape. The four shaft heads 20 are evenly divided into two groups. The two shaft heads 20 in the same group are located on the same axis. The two groups of shaft heads 20 respectively cooperate with two external universal joint forks to form the core transmission unit in the automobile chassis, realizing the variable angle power transmission function of the cross-shaft universal joint.

[0030] The shaft head 20 is integrally formed with the shaft body 10, avoiding the additional weight and stress concentration caused by welding and other connection methods, thus making the overall strength of the cross shaft greater. The shaft head 20 includes a journal 21, a first convex ring 22, and a second convex ring 23. The journal 21, the first convex ring 22, and the second convex ring 23 are coaxially arranged. The diameter of the journal 21 is smaller than the diameter of the first convex ring 22, and the diameter of the first convex ring 22 is smaller than the diameter of the second convex ring 23. This results in the diameters of the journal 21, the first convex ring 22, and the second convex ring 23 increasing sequentially. The first convex ring 22 and the second convex ring 23 are located at the end of the journal 21 near the shaft body 10, and the second convex ring 23 is located on the side of the first convex ring 22 near the shaft body 10. This results in the diameters of the journal 21, the first convex ring 22, and the second convex ring 23 gradually increasing from the journal 21 towards the shaft body 10. Because the shaft head 20 is integrally formed with the shaft body 10 and made of the same material, the upper limits of the stress and torque that the above three parts can withstand increase sequentially. By setting the first convex ring 22 and the second convex ring 23 in this way, the torque received by the journal 21 can be transferred to the shaft body 10, reducing the sudden change in the maximum torque borne by the journal 21 and the shaft body 10, and improving the overall strength of the cross shaft.

[0031] Multiple reinforcing ribs 30 are provided. These reinforcing ribs 30 are distributed between adjacent shaft ends 20. During the rotation of the cross shaft, adjacent shaft ends 20 are subjected to stress and torque transmitted from the external universal joint fork. This arrangement allows the shaft body 10 area located between adjacent shaft ends 20 to withstand greater stress, thereby increasing the strength of the weak area where stress is concentrated at the connection between the shaft end 20 and the shaft body 10, and reducing localized high stress caused by sudden changes in root force when the shaft end 20 is subjected to force.

[0032] The surface of the shaft body 10 is a forged blank surface, the surfaces of the journal 21 and the first convex ring 22 are ground and finished surfaces, and the surface of the second convex ring 23 is a machined surface. Since the processing techniques for these four parts are not entirely the same, and given the same material dimensions, materials with lower processing precision generally have lower strength, to achieve a design with equal strength, the diameter of parts with lower processing precision needs to be larger. This is one of the reasons why the diameters of the journal 21, the first convex ring 22, and the second convex ring 23 are set to increase sequentially. Therefore, compared to thickening the entire shaft body 10 and shaft head 20 to increase strength, adding reinforcing ribs 30 only in critical stress areas can improve strength without significantly increasing the overall size and weight of the cross shaft, conforming to the trend of lightweight design.

[0033] The reinforcing ribs 30 are arranged around the axis of the shaft body 10 along their length direction, corresponding to the distribution of the shaft head 20 along the circumference of the shaft body 10, forming a ring-shaped reinforcing structure that is evenly distributed along the circumference. This can evenly transfer the torque and stress borne by the shaft head 20 to the shaft body 10, avoid excessive local structural load, and improve the overall strength of the cross shaft.

[0034] like Figure 4 As shown, the surface of the reinforcing rib 30 includes a first curved surface 31. A reference section passes through the axis of the shaft body 10 and extends through a portion of the reinforcing rib 30. In the reference section, the line connecting the midpoint of the section line of the first curved surface 31 to the geometric center is the reference line 40, and the angle between the reference line 40 and the axis of the shaft body 10 is acute. If the reinforcing rib 30 is placed at the shortest distance between adjacent shaft ends 20 on the shaft body 10, the angle between the reference line 40 and the axis of the shaft body 10 is right-angled. This section of the reinforcing rib 30 is relatively short, limiting its strength enhancement. Furthermore, the strength enhancement provided by this section of the reinforcing rib 30 for the gap position between adjacent shaft ends 20 on the shaft body 10 is clearly greater than the strength enhancement provided by the reinforcing rib 30 for the journal 21, the first convex ring 22, the second convex ring 23, and parts of the shaft body 10 far from this gap position. This is detrimental to the equal strength design of the reinforced universal joint cross shaft.

[0035] The present invention sets the angle between the reference line 40 and the axis of the shaft body 10 to an acute angle, which can extend the length of the reinforcing rib 30 on the shaft body 10. Under the combined stress scenario, the reinforcing rib 30 can distribute the stress along the inclined direction to a larger area on the shaft body 10. This can improve the strength of the journal 21, the first convex ring 22, the second convex ring 23 and the opening position on the shaft body 10 between adjacent shaft heads 20 to a similar degree, minimize the mass difference of the journal 21, the first convex ring 22, the second convex ring 23 and the opening position, improve the overall strength of the cross shaft while ensuring that the strength of each part is close to equal.

[0036] Furthermore, such as Figure 2 As shown, the axis of the shaft body 10 is perpendicular to the central plane 50, and the geometric center point is located within the central plane 50. In the reference section, the center of the cross-section line of the first curved surface 31 is located on the side of the reference line 40 near the central plane 50, and the reference line 40 passes through the midpoint and the geometric center point of the cross-section line of the first curved surface 31. This makes the average height of the reinforcing rib 30 protruding from the surface of the shaft body 10 on the side near the central plane 50 higher. Furthermore, because the reinforcing rib 30 is located between adjacent shaft ends 20, it further enhances the strength of the journal 21, the first convex ring 22, the second convex ring 23, and the opening position on the shaft body 10 located between adjacent shaft ends 20. This improves the overall strength of the cross shaft while ensuring that each part tends to have equal strength.

[0037] Furthermore, such as Figure 3 As shown, the angle α1 between the reference line 40 and the central plane 50 is within the range of 24° to 30°. Finite element static strength analysis of the cross shaft in this embodiment shows that when α1 is set within the range of 24° to 30°, under the same torque load, the maximum equivalent stress of the cross shaft decreases more significantly than when set within other acute angle ranges, thus resulting in a greater overall strength improvement for the cross shaft.

[0038] Preferably, α1 can be set to 27.4°. Under the same torque load, the maximum equivalent stress of the cross shaft decreases the most, and the overall strength of the cross shaft increases the most.

[0039] Furthermore, such as Figure 4 As shown, the surface of the reinforcing rib 30 also includes a first plane 32 and a second plane 33. A first curved surface 31 is located between the first plane 32 and the second plane 33, with the first plane 32 located on the side of the first curved surface 31 away from the central plane 50. Figure 4As shown, in the reference section, the length of the section line of the first plane 32 is less than the length of the section line of the second plane 33. The section lines of the first plane 32 and the second plane 33 are marked with red lines. This arrangement further expands the width of the reinforcing rib 30 in the direction of the opening between adjacent shafts, ultimately improving the overall strength of the cross shaft while ensuring that each part tends to have equal strength.

[0040] Furthermore, such as Figure 4 As shown, the surface of the reinforcing rib 30 also includes two transition surfaces 34. One transition surface 34 is located between the first plane 32 and the surface of the shaft body 10, and the other transition surface 34 is located between the second plane 33 and the surface of the shaft body 10. This arrangement allows for a smooth transition between the first plane 32, the second plane 33, and the shaft body 10, avoiding stress concentration areas and reducing machining difficulty.

[0041] Furthermore, such as Figure 3 and Figure 4 As shown, the angle β1 between the first plane 32 and the central plane 50 is between 4° and 10°. Finite element static strength analysis of the cross shaft in this embodiment shows that when β1 is set within the range of 4° to 10°, under the same torque load, the maximum equivalent stress of the cross shaft decreases more significantly than when set within other angle ranges, thus resulting in a greater overall strength improvement for the cross shaft.

[0042] Preferably, β1 can be set to 5°. Under the same torque load, the maximum equivalent stress of the cross shaft decreases the most, and the overall strength of the cross shaft increases the most.

[0043] Furthermore, such as Figure 3 and Figure 4 As shown, the angle β2 between the second plane 33 and the axis of the shaft body 10 is between 11° and 17°. After performing finite element static strength analysis on the cross shaft in this embodiment, it was found that when β2 is set in the range of 11° to 17°, under the premise of loading the same torque, the maximum equivalent stress of the cross shaft decreases more than when it is set in other angle ranges, thus making the overall strength of the cross shaft more improved.

[0044] Preferably, β2 can be set to 14°. Under the same torque load, the maximum equivalent stress of the cross shaft decreases the most, and the overall strength of the cross shaft increases the most.

[0045] In other embodiments, β2 can be set to twice β1 to improve the overall strength of the cross shaft.

[0046] Furthermore, such as Figure 1 and Figure 4As shown, the height L1 of the reinforcing rib 30 protruding from the surface of the shaft body 10 is 1mm to 2mm. Finite element static strength analysis of the cross shaft in this embodiment shows that when L1 is set within the range of 1mm to 2mm, under the same torque load, the maximum equivalent stress of the cross shaft decreases more significantly than when set within other height ranges, thus resulting in a greater overall strength improvement. Furthermore, this setting minimizes the weight change of the cross shaft, meeting the requirements of lightweight design.

[0047] Preferably, L1 can be set to 1.25mm. Under the same torque load, the maximum equivalent stress of the cross shaft decreases the most, and the overall strength of the cross shaft increases the most.

[0048] Furthermore, such as Figure 1 As shown, four reinforcing ribs 30 form a group. Each group of reinforcing ribs 30 is concentrically arranged, corresponding to the longitudinal direction of the reinforcing ribs 30 surrounding the axis of the shaft body 10. There are two groups of reinforcing ribs 30 arranged along the axial direction of the shaft body 10, and these two groups of reinforcing ribs 30 can be symmetrically arranged on both sides of the central plane. This makes the strength enhancement effect of the reinforcing ribs 30 more comprehensive and stable, effectively avoiding stress transfer, and thus improving the overall strength of the cross shaft while ensuring the equal strength design.

[0049] Furthermore, such as Figure 5 As shown, the reinforced universal joint cross shaft also includes bearings 60. Four bearings 60 are provided, each corresponding to a shaft head 20, and each bearing 60 is fitted onto the journal 21. The surface of the shaft head 20 mates with the inner ring of the bearing 60, and the outer ring of the bearing 60 mates with the external universal joint fork shaft hole, achieving low-friction rotation. The first convex ring 22 and the second convex ring 23 can restrict the axial displacement of the bearing 60, preventing loosening and ensuring the stability of torque transmission.

[0050] Furthermore, the bearing 60 can be configured as a needle roller bearing 60. The needle roller bearing 60 has a smaller radial cross-sectional dimension, enabling reliable support at the cross shaft journal 21 where the radial space is narrow. Moreover, compared to other bearings 60 with the same load-bearing capacity, the needle roller bearing 60 has slender needles, a simplified structure, uses less material, and is lighter overall, meeting the requirements of lightweight design.

[0051] Finite element static strength analysis was performed to compare the state of the universal joint cross shaft before and after the improvement in this embodiment. Before the improvement, the cross shaft was in a state without reinforcing ribs, and after the improvement, it was in a state with reinforcing ribs. The parameters of the reinforcing ribs were: α1 set to 27.4°, β1 set to 5°, β2 set to 14°, and L1 set to 1.25mm. Under the same torque, the maximum equivalent stress of the universal joint cross shaft before the improvement was 813MPa, and the maximum equivalent stress after the improvement was 791MPa, a decrease of 2.7%. The maximum equivalent stress values ​​of each part of the shaft body 10, the first convex ring 22, the second convex ring 23, and the journal 21, as well as the entire universal joint cross shaft, are shown in the table below. The maximum equivalent stress values ​​of each part decreased to varying degrees, and the strength of each part was correspondingly improved, thus improving the overall strength of the universal joint cross shaft. At the same time, the strength improvement of the first convex ring 22 and the journal 21 was relatively large. This allows for control over the fracture location of the universal joint cross shaft in the static torsional strength destructive test during structural design, thereby facilitating the overall strength structural design of the universal joint cross shaft.

[0052] The table below compares the maximum equivalent stress data from finite element static strength analysis before and after the cross shaft improvement:

[0053]

[0054] The experimental results show that while improving the strength of the cross shaft, the weight of the cross shaft before the improvement was 3.3179 kg, and after the improvement it was 3.3225 kg, with a weight change of only 0.14%. This has a very small impact on the weight of the parts and meets the requirements of lightweight design.

[0055] Those skilled in the art will understand that the above embodiments are specific examples of implementing this disclosure, and in practical applications, various changes can be made in form and detail without departing from the scope of this disclosure.

Claims

1. A reinforced universal joint cross shaft, characterized in that, The reinforced universal joint cross shaft includes: The shaft body has its geometric center at the midpoint of its own axial direction; the surface of the shaft body is a forged blank surface. The shaft head comprises four shaft heads distributed circumferentially along the shaft body; the axis of each shaft head is perpendicular to the axis of the shaft body; the projection of the four shaft heads along the axial direction of the shaft body forms a cross shape; the shaft head is integrally formed with the shaft body; each shaft head includes a journal, a first convex ring, and a second convex ring; the journal, the first convex ring, and the second convex ring are coaxially arranged; the diameter of the journal is smaller than the diameter of the first convex ring; the diameter of the first convex ring is smaller than the diameter of the second convex ring; the first convex ring and the second convex ring are located at the end of the journal near the shaft body; the second convex ring is located on the side of the first convex ring near the shaft body; the surfaces of the journal and the first convex ring are both ground and finished surfaces; the surface of the second convex ring is machined surface. A plurality of reinforcing ribs are provided; the plurality of reinforcing ribs are distributed between adjacent shaft ends; the length direction of the reinforcing ribs is arranged around the axis of the shaft body; the surface of the reinforcing ribs includes a first curved surface; a reference section passes through the axis of the shaft body; the reference section passes through a portion of the reinforcing ribs; in the reference section, the line connecting the midpoint of the cross-section line of the first curved surface to the geometric center point is a reference line; the angle between the reference line and the axis of the shaft body is an acute angle.

2. The reinforced universal joint cross shaft according to claim 1, characterized in that, The axis of the shaft body is perpendicular to the central plane, and the geometric center point is located in the central plane; in the reference section, the center of the cross-section line of the first curved surface is located on the side of the reference line closer to the central plane.

3. The reinforced universal joint cross shaft according to claim 2, characterized in that, The angle between the reference line and the central plane is between 24° and 30°.

4. The reinforced universal joint cross shaft according to claim 2, characterized in that, The surface of the reinforcing rib further includes a first plane and a second plane; the first curved surface is located between the first plane and the second plane; the first plane is located on the side of the first curved surface away from the central plane; in the reference cross-section, the length of the cross-sectional line of the first plane is less than the length of the cross-sectional line of the second plane.

5. A reinforced universal joint cross shaft according to claim 4, characterized in that, The surface of the reinforcing rib also includes two transition surfaces; one of the transition surfaces is located between the first plane and the surface of the shaft body, and the other transition surface is located between the second plane and the surface of the shaft body.

6. The reinforced universal joint cross shaft according to claim 4, characterized in that, The angle between the first plane and the central plane is between 4° and 10°.

7. The reinforced universal joint cross shaft according to claim 4, characterized in that, The angle between the second plane and the axis of the shaft body is between 11° and 17°.

8. The reinforced universal joint cross shaft according to claim 1, characterized in that, The reinforcing rib protrudes from the surface of the shaft body at a height of 1mm to 2mm.

9. A reinforced universal joint cross shaft according to claim 1, characterized in that, The four reinforcing ribs form a group; each group of reinforcing ribs is concentrically arranged; there are two groups of reinforcing ribs arranged along the axial direction of the shaft body.

10. A reinforced universal joint cross shaft according to claim 1, characterized in that, The reinforced universal joint cross shaft also includes bearings; four bearings are provided; each bearing is provided in a one-to-one correspondence with the shaft head; the bearings are sleeved on the journal.

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