Method for grinding outer circle of ball cage shaft

Abstract

The invention relates to the technical field of driving shafts, in particular to a ball cage shaft outer circle grinding method. The ball cage shaft outer circle grinding method comprises the steps that a ball cage shaft is positioned in the positioning assembly; on the basis that positioning of the ball cage shaft is completed, the ball cage shaft is controlled to rotate; based on the rotating state of the ball cage shaft, a grinding wheel is controlled to rotate; on the basis that the grinding wheel is in the rotating state, the grinding wheel is moved to a machining position, so that a first grinding face on the grinding wheel abuts against the first peripheral face, and a second grinding face on the grinding wheel abuts against the second peripheral face; on the basis that grinding of the first peripheral face and the second peripheral face is completed, the grinding wheel is controlled to move till the grinding wheel abuts against the third peripheral face; and on the basis that machining of the third peripheral face is completed, grinding machining of the outer circle of the ball cage shaft is completed. Therefore, the problem that time consumed by repeated grinding of the outer circle of the ball cage shaft is long is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of drive shafts, and in particular to a method for grinding the outer circle of a cage shaft. Background Art

[0002] The driveshaft is a rigid shaft connecting the differential and wheels in a car. Its core function is to transmit torque, transferring engine power, reduced in speed by the transmission, directly to the drive wheels. Universal joints are key components in automotive drivetrains, enabling variable-angle power transmission between rotating shafts. Located at the end of the driveshaft, they connect the driveshaft to the drive axle, half-shafts, and other components. As a vehicle moves, the wheels experience shifts in angle and distance due to steering and suspension compression. Conventional rigid shafts cannot accommodate this dynamic misalignment. Therefore, universal joints are required at both ends of the driveshaft to achieve both torque transmission and angle compensation. The ball joint (BJJ) is a type of universal joint widely used in automotive driveshafts due to its high transmission efficiency, wide range of allowable rotation angles, and stable performance at high speeds. A BJJ joint consists of a ball joint housing, bell housing, steel balls, retainer, dust cover, and other components.

[0003] The ball cage shaft is a shaft structure integrally molded with the cage housing. It serves as the extended portion of the ball cage universal joint, transmitting power. One end is connected to the joint's core structure, and the other can be connected to a drive shaft or other transmission component, furthering the joint's power output. During machining, the ball cage shaft typically requires grinding multiple peripheral surfaces of varying diameters. This requires multiple tool retractions, resulting in low machining efficiency. Improving grinding efficiency is a pressing issue. Summary of the Invention

[0004] In order to solve the problem that multiple grinding of the outer circle of the ball cage shaft takes a long time and three grinding of the outer circle of the ball cage shaft takes a long time, the present invention provides a method for grinding the outer circle of the ball cage shaft, comprising:

[0005] Positioning the cage shaft in the positioning assembly; the cage shaft comprises an integrally formed cage housing and a shaft; the shaft comprises a first outer peripheral surface, a second outer peripheral surface, and a third outer peripheral surface; the second outer peripheral surface is located between the first outer peripheral surface and the third outer peripheral surface; when the cage shaft is positioned in the positioning assembly, the shaft coincides with the positioning axis;

[0006] Based on the completion of positioning of the ball cage shaft, controlling the rotation of the ball cage shaft;

[0007] Based on the cage shaft being in a rotating state, the grinding wheel is controlled to rotate; the grinding wheel has a first grinding surface and a second grinding surface; the distance from the first grinding surface to the positioning axis is a first distance; the distance from the second grinding surface to the positioning axis is a second distance; the first distance and the second distance have a difference;

[0008] Based on the grinding wheel being in a rotating state, moving the grinding wheel to a processing position so that the first grinding surface of the grinding wheel abuts against the first outer peripheral surface, and the second grinding surface abuts against the second outer peripheral surface;

[0009] Based on the completion of grinding the first outer peripheral surface and the second outer peripheral surface, controlling the grinding wheel to move until the grinding wheel abuts against the third outer peripheral surface;

[0010] Based on the completion of the machining of the third outer peripheral surface, the outer cylindrical grinding of the ball cage shaft is completed.

[0011] In some embodiments, the first outer peripheral surface is located on a side of the second outer peripheral surface close to the cage shell.

[0012] In some embodiments, the first distance is greater than the second distance;

[0013] The method of controlling the grinding wheel to move until the grinding wheel abuts against the third outer peripheral surface based on the completion of grinding the first outer peripheral surface and the second outer peripheral surface comprises:

[0014] Based on the completion of grinding the first outer peripheral surface and the second outer peripheral surface, the grinding wheel is controlled to move until the second grinding surface abuts against the third outer peripheral surface.

[0015] In some embodiments, the cylindrical grinding method of the cage shaft further comprises:

[0016] Based on the completion of the cylindrical grinding of the ball cage shaft, the number of processed pieces is accumulated;

[0017] Based on the fact that the number of processed pieces is less than the first preset number of pieces, the step of positioning the cage shaft in the positioning assembly is returned to for the next cage shaft to be ground.

[0018] In some embodiments, the cylindrical grinding method of the cage shaft further comprises:

[0019] Based on the number of processed pieces reaching the first preset number of pieces, dressing the second grinding surface;

[0020] Upon completion of the finishing of the second grinding surface, the process returns to the step of positioning the cage shaft in the positioning assembly for the next cage shaft to be ground.

[0021] In some embodiments, the cylindrical grinding method of the cage shaft further comprises:

[0022] Based on the number of processed pieces reaching a second preset number of pieces, the first grinding surface and the second grinding surface are simultaneously trimmed; the second preset number of pieces is greater than the first preset number of pieces;

[0023] Based on the completion of the dressing of the first grinding surface, the number of workpieces is reset to zero, and for the next cage shaft to be ground, the process returns to the step of positioning the cage shaft in the positioning assembly.

[0024] In some embodiments, when the first grinding surface and the second grinding surface are simultaneously finished, a difference between an upper limit of the tolerance range of the first distance and an upper limit of the tolerance range of the first outer peripheral surface is smaller than a first threshold.

[0025] In some embodiments, when the first grinding surface and the second grinding surface are simultaneously finished, a difference between a lower limit of the tolerance range of the second distance and a lower limit of the tolerance range of the second outer peripheral surface is smaller than a second threshold.

[0026] In some embodiments, the axial length of the first outer peripheral surface is smaller than the axial length of the second outer peripheral surface;

[0027] A length of the first grinding surface along the positioning axis is shorter than a length of the second grinding surface along the positioning axis.

[0028] In some embodiments, the first grinding surface and the second grinding surface are both conical surfaces; and the angle between the axis of the grinding wheel and the positioning axis is an acute angle.

[0029] In order to solve the problem of time-consuming multiple grinding of the outer circle of the cage shaft, the present invention has the following advantages:

[0030] By positioning the first grinding surface of the grinding wheel against the first peripheral surface and the second grinding surface against the second peripheral surface, the first and second peripheral surfaces can be ground simultaneously. Once the first and second peripheral surfaces are machined, only one tool retraction is required before proceeding to the next grinding step. Compared to grinding the first and second peripheral surfaces once, and then retracting the tool twice after grinding, this approach saves one grinding and one tool retraction, significantly improving grinding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic flow chart of a method for grinding the outer cylindrical surface of a cage shaft according to an embodiment is shown;

[0032] Figure 2 Shows the application Figure 1 The structural diagram of the device for the ball cage shaft external cylindrical grinding method;

[0033] Figure 3 Shown Figure 2 Partial cross-sectional view of the ball cage shaft in.

[0034] Reference numerals: 10 grinding assembly; 11 grinding wheel; 12 first driving portion; 13 first grinding surface; 14 second grinding surface; 20 positioning assembly; 30 ball cage shaft; 31 ball cage housing; 32 shaft; 33 first outer peripheral surface; 34 second outer peripheral surface; 35 third outer peripheral surface. DETAILED DESCRIPTION

[0035] 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 implement the present disclosure, rather than to imply any limitation on the scope of the present disclosure.

[0036] As used herein, the term "including" 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 "based, at least in part, 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." Terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "vertical," "horizontal," "transverse," and "longitudinal" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily intended to better describe the present application and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed and operated in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientation or positional relationships. For example, the term "on" may, in certain circumstances, be used to indicate a dependency or connection relationship. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances. Furthermore, the terms "installed," "disposed," "provided with," "connected," and "connected" are to 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, an indirect connection through an intermediate medium, or an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, 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 specified, "plurality" means two or more.

[0037] Example 1:

[0038] The drive shaft is a rigid shaft connecting the differential and wheels in a car. Its core function is to transmit torque, transferring the engine's power, which has been decelerated and torque-increased by the gearbox, directly to the drive wheels. Universal joints are key components in a car's transmission system, enabling variable-angle power transmission between rotating shafts. Because the wheels change angle and distance due to steering and suspension compression while the vehicle is in motion, ordinary rigid shafts cannot adapt to this dynamic misalignment. Therefore, universal joints must be used at both ends of the drive shaft to achieve the dual functions of torque transmission and angle compensation. A ball joint is a type of universal joint that includes a ball joint housing 31, a bell housing, steel balls, a retaining cage, a dust cover, and other components.

[0039] The cage shaft 30 is a shaft 32 structure integrally formed with the cage housing 31. The cage shaft 30 has multiple peripheral surfaces that need to be ground. Grinding multiple peripheral surfaces requires multiple tool retractions, resulting in low processing efficiency. How to improve grinding efficiency is currently an urgent problem to be solved.

[0040] In this embodiment, if Figure 1 As shown, a method for grinding the outer cylindrical surface of a cage shaft 30 includes steps S10 to S60, which are specifically described as follows:

[0041] Step S10: Figure 2 As shown, the ball cage shaft 30 is positioned in the positioning assembly 20; Figure 3 As shown, the cage shaft 30 includes an integrally formed cage housing 31 and a shaft 32. The shaft 32 has a first outer peripheral surface 33, a second outer peripheral surface 34, and a third outer peripheral surface 35. The second outer peripheral surface 34 is located between the first outer peripheral surface 33 and the third outer peripheral surface 35. Thus, the first outer peripheral surface 33 and the second outer peripheral surface 34 are adjacent to each other, which can reduce the distance between the first grinding surface 13 and the second grinding surface 14 of the grinding wheel 11 along the positioning axis, thereby reducing the volume of the grinding wheel 11 and lowering equipment costs. When the cage shaft 30 is positioned in the positioning assembly 20, the shaft 32 coincides with the positioning axis.

[0042] Step S20: Based on the positioning of the cage shaft 30, the cage shaft 30 is controlled to rotate. This allows the cage shaft 30 to rotate about the axis of its own shaft 32, i.e., the positioning axis, after positioning. This reduces the difficulty and time required for grinding, rather than requiring the cage shaft 30 to remain stationary after grinding begins.

[0043] Step S30: Based on the cage shaft 30 being in a rotating state, control the grinding wheel 11 to rotate; Figure 2As shown, the grinding assembly 10 includes a grinding wheel 11 and a first drive unit 12. The grinding wheel 11 has a first grinding surface 13 and a second grinding surface 14. The first grinding surface 13 and the second grinding surface 14 form a stepped shape. The distance from the first grinding surface 13 to the positioning axis is a first distance; the distance from the second grinding surface 14 to the positioning axis is a second distance. These first and second distances correspond to the radii of the first and second outer peripheral surfaces 33 and 34, respectively. The first and second distances have a difference, thereby adapting to the difference in the radii of the first and second outer peripheral surfaces 33 and 34.

[0044] Step S40: While the grinding wheel 11 is rotating, the grinding wheel 11 is moved to a processing position so that the first grinding surface 13 of the grinding wheel 11 abuts the first outer peripheral surface 33, and the second grinding surface 14 abuts the second outer peripheral surface 34. This allows the first outer peripheral surface 33 and the second outer peripheral surface 34 to be ground simultaneously, and only one back-off is required after the grinding is completed before proceeding to the next grinding step. Compared to grinding the first outer peripheral surface 33 and the second outer peripheral surface 34 once, and then backing off twice after the grinding is completed, this method saves the time of one grinding and one back-off, significantly improving the efficiency of the grinding process.

[0045] Step S50: Based on the completion of grinding of the first outer peripheral surface 33 and the second outer peripheral surface 34, the grinding wheel 11 is controlled to move until the grinding wheel 11 abuts the third outer peripheral surface 35; since the cage shaft 30 and the grinding wheel 11 are always in a rotating state, the third outer peripheral surface 35 can be ground after abutment.

[0046] Step S60 : Based on the completion of machining of the third outer peripheral surface 35 , the outer cylindrical grinding of the cage shaft 30 is completed.

[0047] Furthermore, if Figure 3 As shown, the first outer peripheral surface 33 is located on the side of the second outer peripheral surface 34 that is closer to the cage housing 31. Because the cage shaft 30 and the grinding wheel 11 abut at two locations when the first and second outer peripheral surfaces 33, 34 are ground simultaneously, the abutment area is large, resulting in a greater abutment force. This arrangement shortens the distance between the points of action of the abutment force on the first and second outer peripheral surfaces 33, 34 and the center of gravity of the cage shaft 30, thereby reducing the torque of the abutment force and ensuring stability during the grinding process.

[0048] Furthermore, if Figure 2 As shown, the first distance is greater than the second distance.

[0049] Upon completion of grinding the first outer peripheral surface 33 and the second outer peripheral surface 34 , the grinding wheel 11 is controlled to move until the grinding wheel 11 abuts against the third outer peripheral surface 35 , including:

[0050] After the grinding of the first outer peripheral surface 33 and the second outer peripheral surface 34 is completed, the grinding wheel 11 is controlled to move until the second grinding surface 14 abuts the third outer peripheral surface 35. Since the second outer peripheral surface 34 is located between the first outer peripheral surface 33 and the third outer peripheral surface 35, and the second distance is smaller than the first distance, the third outer peripheral surface 35 is ground by the second grinding surface 14. As a result, during the movement of the grinding wheel 11, the possibility of interference between the first grinding surface 13 and other parts of the shaft 32 is reduced, thereby improving the rationality of the structural design.

[0051] Furthermore, the cylindrical grinding method of the cage shaft 30 further includes step S70; step S70 includes steps S71 to S72:

[0052] Step S71: Based on the completion of the cylindrical grinding of the cage shaft 30, the number of processed parts is accumulated;

[0053] Step S72 : Based on the fact that the number of processed pieces is less than the first preset number of pieces, the process returns to the step of positioning the cage shaft 30 in the positioning assembly 20 for the next cage shaft 30 to be ground.

[0054] In this way, when the number of processed pieces does not reach the first preset number, after completing the outer surface processing of one cage shaft 30, the processing of the next cage shaft 30 can be automatically started, thereby realizing the cycle of the grinding process of the outer circle of the cage shaft 30.

[0055] Furthermore, the cylindrical grinding method of the cage shaft 30 further includes step S80; step S80 includes step S81 and step S82:

[0056] Step S81: trimming the second grinding surface 14 based on the number of processed pieces reaching a first preset number of pieces;

[0057] Step S82 : Based on the completion of the trimming of the second grinding surface 14 , for the next cage shaft 30 to be ground, the process returns to the step of positioning the cage shaft 30 in the positioning assembly 20 .

[0058] In the above-described cylindrical grinding method for the cage shaft 30, the second grinding surface 14 is used more frequently than the first grinding surface 13. Therefore, the second grinding surface 14 is used more frequently than the first grinding surface 13, so it reaches the trimming threshold first. This arrangement allows the cylindrical grinding process of the cage shaft 30 to be accurately stopped when the number of processed pieces reaches the first predetermined number, allowing the second grinding surface 14 to be trimmed, thereby ensuring the quality of subsequent machining of the cage shaft 30.

[0059] Furthermore, the cylindrical grinding method of the cage shaft 30 further includes step S90; step S90 includes step S91 and step S92:

[0060] Step S91: Based on the number of processed pieces reaching a second preset number of pieces, the first grinding surface 13 and the second grinding surface 14 are simultaneously trimmed; the second preset number of pieces is greater than the first preset number of pieces;

[0061] Step S92: Based on the completion of the dressing of the first grinding surface 13, the number of workpieces is reset to zero, and for the next cage shaft 30 to be ground, the process returns to the step of positioning the cage shaft 30 in the positioning assembly 20.

[0062] In this way, when the number of times the first grinding surface 13 is used, that is, the second preset number of pieces reaches the threshold, the first grinding surface 13 and the second grinding surface 14 can be trimmed at the same time, reducing the number of shutdowns caused by trimming and improving processing efficiency.

[0063] In other embodiments, the second predetermined number of pieces can be approximately twice the first predetermined number of pieces. Since the second grinding surface 14 is used twice as many times as the first grinding surface 13 after completing any number of cycles of the cylindrical grinding method for the cage shaft 30, setting the second predetermined number of pieces to approximately twice the first predetermined number of pieces based on this quantitative relationship minimizes the number of machine downtimes required for repairs, thereby improving processing efficiency.

[0064] Furthermore, if Figure 2 As shown, when the first grinding surface 13 and the second grinding surface 14 are simultaneously dressed, the difference between the upper limit of the tolerance range of the first distance and the upper limit of the tolerance range of the first outer peripheral surface 33 is less than the first threshold.

[0065] Because the second grinding surface 14 is used twice as often as the first grinding surface 13 after any number of complete cycles of the above-described cylindrical grinding method for the cage shaft 30, the second grinding surface 14 of the grinding wheel 11 experiences greater wear than the first grinding surface 13. As the number of grinding operations and the number of dressing operations gradually increase, the difference between the second distance and the first distance gradually decreases. As the number of dressing operations reaches a certain level, the difference between the second distance and the first distance becomes too small, requiring a significant adjustment to the depth of the first grinding surface 13 to ensure the depth of the step formed by the first and second grinding surfaces 13, 14. Furthermore, trimming the step depth takes significantly more time than cleaning the outer surface.

[0066] By setting the difference between the upper limit of the tolerance range of the first distance and the upper limit of the tolerance range of the first outer peripheral surface 33 to be less than the first threshold value, the first distance is maintained in a larger range after trimming, and the design depth of the step is made as large as possible, which can reduce the number of times the step depth is trimmed, so that more trimming times are used to clean foreign matter on the surfaces of the first grinding surface 13 and the second grinding surface 14, rather than trimming the step depth, thereby enabling the present invention to save trimming time.

[0067] Furthermore, if Figure 2As shown, when the first grinding surface 13 and the second grinding surface 14 are simultaneously dressed, the difference between the lower limit of the tolerance range of the second distance and the lower limit of the tolerance range of the second outer peripheral surface 34 is less than the second threshold.

[0068] By setting the difference between the lower limit of the tolerance range of the second distance and the lower limit of the tolerance range of the second outer peripheral surface 34 to be smaller than the second threshold, the second distance is kept in a smaller range after trimming, so that the design depth of the step is as large as possible, and a lot of trimming time is saved.

[0069] Furthermore, if Figure 3 As shown, the axial length of the first outer peripheral surface 33 is shorter than the axial length of the second outer peripheral surface 34; this can reduce the thickness of the grinding wheel 11. The length of the first grinding surface 13 along the positioning axis is shorter than the length of the second grinding surface 14 along the positioning axis. This makes the second grinding surface 14 longer along the positioning axis, allowing the second grinding surface 14 to grind the second outer peripheral surface 34 and the third outer peripheral surface 35 of different axial lengths, thereby improving adaptability.

[0070] Furthermore, if Figure 2 As shown, both the first grinding surface 13 and the second grinding surface 14 are tapered surfaces. While maintaining the contact area between the grinding wheel 11 and the cage shaft 30, this design reduces the thickness of the grinding wheel 11 compared to a cylindrical outer surface, thereby reducing costs. The acute angle between the axis of the grinding wheel 11 and the positioning axis shortens the moment arm of the contact force from the cage shaft 30, thereby reducing the torque applied to the grinding wheel 11 and, consequently, minimizing damage to the grinding wheel 11.

[0071] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present disclosure, and that in actual applications, various changes may be made thereto in form and detail without departing from the scope of the present disclosure.

Claims

1. A method for grinding the outer cylindrical surface of a ball cage shaft, characterized in that: The cylindrical grinding method of the ball cage shaft comprises: Positioning the cage shaft in the positioning assembly; the cage shaft comprises an integrally formed cage housing and a shaft; the shaft comprises a first outer peripheral surface, a second outer peripheral surface, and a third outer peripheral surface; the second outer peripheral surface is located between the first outer peripheral surface and the third outer peripheral surface; when the cage shaft is positioned in the positioning assembly, the shaft coincides with the positioning axis; Based on the completion of positioning of the ball cage shaft, controlling the rotation of the ball cage shaft; Based on the cage shaft being in a rotating state, the grinding wheel is controlled to rotate; the grinding wheel has a first grinding surface and a second grinding surface; the distance from the first grinding surface to the positioning axis is a first distance; the distance from the second grinding surface to the positioning axis is a second distance; the first distance and the second distance have a difference; Based on the grinding wheel being in a rotating state, moving the grinding wheel to a processing position so that the first grinding surface of the grinding wheel abuts against the first outer peripheral surface, and the second grinding surface abuts against the second outer peripheral surface; Based on the completion of grinding the first outer peripheral surface and the second outer peripheral surface, controlling the grinding wheel to move until the grinding wheel abuts against the third outer peripheral surface; Based on the completion of the machining of the third outer peripheral surface, the outer cylindrical grinding of the ball cage shaft is completed.

2. A method for grinding the outer cylindrical surface of a cage shaft according to claim 1, characterized in that: The first outer peripheral surface is located on a side of the second outer peripheral surface close to the cage shell.

3. The method for grinding the outer cylindrical surface of a cage shaft according to claim 1, wherein: The first distance is greater than the second distance; The method of controlling the grinding wheel to move until the grinding wheel abuts against the third outer peripheral surface based on the completion of grinding the first outer peripheral surface and the second outer peripheral surface comprises: Based on the completion of grinding the first outer peripheral surface and the second outer peripheral surface, the grinding wheel is controlled to move until the second grinding surface abuts against the third outer peripheral surface.

4. A method for grinding the outer cylindrical surface of a cage shaft according to claim 3, characterized in that: The ball cage shaft external cylindrical grinding method also includes: Based on the completion of the cylindrical grinding of the ball cage shaft, the number of processed pieces is accumulated; Based on the fact that the number of processed pieces is less than the first preset number of pieces, the step of positioning the cage shaft in the positioning assembly is returned to for the next cage shaft to be ground.

5. A method for grinding the outer cylindrical surface of a cage shaft according to claim 4, characterized in that: The ball cage shaft external cylindrical grinding method also includes: Based on the number of processed pieces reaching the first preset number of pieces, dressing the second grinding surface; Upon completion of the finishing of the second grinding surface, the process returns to the step of positioning the cage shaft in the positioning assembly for the next cage shaft to be ground.

6. A method for grinding the outer cylindrical surface of a cage shaft according to claim 5, characterized in that: The ball cage shaft external cylindrical grinding method also includes: Based on the number of processed pieces reaching a second preset number of pieces, the first grinding surface and the second grinding surface are simultaneously trimmed; the second preset number of pieces is greater than the first preset number of pieces; Based on the completion of the dressing of the first grinding surface, the number of workpieces is reset to zero, and for the next cage shaft to be ground, the process returns to the step of positioning the cage shaft in the positioning assembly.

7. A method for grinding the outer cylindrical surface of a cage shaft according to claim 6, characterized in that: When the first grinding surface and the second grinding surface are simultaneously dressed, a difference between an upper limit of a tolerance range of the first distance and an upper limit of a tolerance range of the first outer peripheral surface is smaller than a first threshold.

8. A method for grinding the outer cylindrical surface of a cage shaft according to claim 7, characterized in that: When the first grinding surface and the second grinding surface are simultaneously dressed, a difference between a lower limit of the tolerance range of the second distance and a lower limit of the tolerance range of the second outer peripheral surface is smaller than a second threshold.

9. The method for grinding the outer cylindrical surface of a cage shaft according to claim 3, wherein: The axial length of the first outer peripheral surface is smaller than the axial length of the second outer peripheral surface; A length of the first grinding surface along the positioning axis is shorter than a length of the second grinding surface along the positioning axis.

10. The method for grinding the outer cylindrical surface of a cage shaft according to claim 1, wherein: The first grinding surface and the second grinding surface are both conical surfaces; and the angle between the axis of the grinding wheel and the positioning axis is an acute angle.

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