Method for forming ball grooves for ball spline shaft

Abstract

A method for forming ball grooves for a ball spline shaft according to one embodiment of the present invention may comprise: a preparation step (S100) of preparing a pipe-shaped material and aligning the center thereof; a pre-heat treatment step (S200) of performing spheroidizing heat treatment on the material having the center aligned; a groove formation step (S300) of forming 12 ball grooves on the material having completed the pre-heat treatment; a post-treatment step (S400) of performing surface treatment and precision inspection on the material having the ball grooves processed; a post-heat treatment step (S500) of performing low-temperature heat treatment on the material having completed the post-treatment; an ultrasonic step (S600) of performing ultrasonic vibration treatment on the material having completed the post-heat treatment; and a quality management step (S700) of managing quality by measuring, with a sensor unit, surface roughness, hardness, residual stress, dimensional accuracy, and surface defects of the material having completed the ultrasonic vibration treatment.

Description

Method for forming ball grooves for ball spline shafts

[0001] The present invention relates to a method for forming ball grooves for a ball spline shaft, and more specifically, to a method for forming ball grooves for a ball spline shaft that increases the number of ball grooves to 12, prevents breakage defects, and simultaneously strengthens durability.

[0002]

[0003] Constant velocity joint components are drive components of a vehicle that serve to protect the driver and the vehicle from the effects of external shocks and vibrations. Among them, spline shafts consist of tubular shafts, solid shafts, balls, ball cages, etc.

[0004] Conventional ball grooves for ball spline shafts are typically formed in six radially. Although durability is enhanced as the number of ball grooves increases, it was difficult to increase the number of ball grooves because a problem of multiple fracture defects occurred during the cold forging stage of forming multiple ball grooves.

[0005] Therefore, research is required on a method for forming ball grooves for a ball spline shaft that increases the number of ball grooves to 12, prevents breakage defects, and simultaneously strengthens durability.

[0006]

[0007] The objective of the present invention is to provide a method for forming ball grooves for a ball spline shaft that increases the number of ball grooves to 12, prevents breakage defects, and simultaneously enhances durability.

[0008]

[0009] A method for forming ball grooves for a ball spline shaft according to an embodiment of the present invention may include a preparation step (S100) of preparing a pipe-shaped material and aligning the center, a pre-heat treatment step (S200) of performing spheroidizing heat treatment on the material with the aligned center, a groove forming step (S300) of forming 12 ball grooves on the material after the pre-heat treatment, a post-treatment step (S400) of performing surface treatment and precision inspection on the material with the ball grooves processed, a post-heat treatment step (S500) of performing low-temperature heat treatment on the material after the post-treatment, an ultrasonic step (S600) of performing ultrasonic vibration treatment on the material after the post-heat treatment, and a quality control step (S700) of managing quality by measuring the surface roughness, hardness, residual stress, dimensional accuracy, and surface defects of the material after the ultrasonic vibration treatment using a sensor unit.

[0010] In addition, after the heat treatment step (S200) according to one embodiment of the present invention, an undercut step (S250) for forming an undercut on the material that has completed the heat treatment may be further included.

[0011] In addition, the post-heat treatment step (S500) according to one embodiment of the present invention may include a heating step (S510) for heating the material after post-treatment, a quenching step (S520) for quenching the heated material with a cooling medium, and a tempering step (S530) for heating the quenched material again to a preset temperature and slowly cooling it.

[0012] In addition, the ultrasonic step (S600) according to one embodiment of the present invention may include a contact step (S610) of contacting the ultrasonic transducer with the material, a setting step (S620) of setting the amplitude and frequency of the ultrasonic vibration of the transducer, a generation step (S630) of generating ultrasonic waves with the transducer, and a cooling step (S640) of cooling the heat generated during the ultrasonic vibration.

[0013] In addition, a method for forming a ball groove for a ball spline shaft according to an embodiment of the present invention further includes a fault diagnosis step of analyzing output data of the sensor unit in real time and determining that a fault has occurred in the sensor unit if the instantaneous rate of change of the output data is greater than or equal to a preset value, wherein the fault diagnosis step comprises the instantaneous rate of change (R) of the output data change Calculate ) and the above instantaneous rate of change (R change ) is a preset limit value (S err If it is greater than ), it is determined that an error has occurred in the sensor's real-time output data, and the instantaneous rate of change (R change ) can be calculated through the derivative f'(x) of the function f(x) representing the characteristics of the sensor unit as shown in [Mathematical Formula 1] below.

[0014] [Mathematical Formula 1]

[0015]

[0016] (Here, R change represents the instantaneous rate of change of the above output data, and △t represents the time change.

[0017]

[0018] A method for forming ball grooves for a ball spline shaft according to one embodiment of the present invention has the effect of increasing the number of ball grooves to 12, preventing breakage defects, and simultaneously strengthening durability.

[0019]

[0020] FIG. 1 is a flowchart illustrating a method for forming a ball groove for a ball spline shaft according to an embodiment of the present invention.

[0021] FIG. 2 is a flowchart illustrating an undercut step according to an embodiment of the present invention.

[0022] FIG. 3 is a flowchart illustrating a post-heat treatment step according to an embodiment of the present invention.

[0023] FIG. 4 is a flowchart illustrating an ultrasonic step according to an embodiment of the present invention.

[0024] FIG. 5 is a diagram illustrating output data of a sensor unit operating normally according to an embodiment of the present invention.

[0025] FIG. 6 is a diagram illustrating output data of a sensor unit operating abnormally according to an embodiment of the present invention.

[0026]

[0027] Specific embodiments of the present invention will be described in detail below with reference to the drawings. However, the concept of the present invention is not limited to the embodiments presented. Those skilled in the art who understand the concept of the present invention may easily propose other inventions that are inferior or other embodiments included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0028] Hereinafter, the method for forming a ball groove for a ball spline shaft according to the present invention will be explained in detail with reference to the attached FIGS. 1 to 4.

[0029]

[0030] FIG. 1 is a flowchart illustrating a method for forming a ball groove for a ball spline shaft according to an embodiment of the present invention.

[0031] Referring to FIG. 1, a method for forming a ball groove for a ball spline shaft according to an embodiment of the present invention may include a preparation step (S100), a pre-heat treatment step (S200), a groove forming step (S300), a post-treatment step (S400), a post-heat treatment step (S500), an ultrasonic step (S600), and a quality control step (S700).

[0032] In the preparation step (S100), a pipe-shaped material can be prepared to align the center. Generally, high-strength alloy steel or stainless steel can be used as the material. Additionally, necessary mechanical equipment such as a CNC milling machine, lathe, and grinder can be prepared, and a dedicated cutter and tool for forming the groove can be prepared.

[0033] In the preheat treatment step (S200), spheroidizing heat treatment can be performed on the material with aligned centers.

[0034]

[0035] Next, we will examine this in more detail with reference to Figure 2.

[0036] FIG. 2 is a flowchart illustrating an undercut step according to an embodiment of the present invention.

[0037] Referring to FIG. 2, also referring to FIG. 2, a method for forming a ball groove for a ball spline shaft according to one embodiment of the present invention may further include an undercut step (S250) after the heat treatment step (S200).

[0038] In the undercut step (S250), an undercut can be formed on the above material after the heat treatment.

[0039]

[0040] Referring again to FIG. 1, in the groove forming step (S300), 12 ball grooves can be formed in the material that has undergone heat treatment. In the groove forming step (S300), a program for forming grooves using a CNC milling machine can be written. The program can be used to accurately set the position, depth, width, and number of grooves. Angles can be set so that the 12 grooves are evenly distributed, and to form 12 grooves, the angle between each groove can be set to 30 degrees (360 degrees ÷ 12). Additionally, a shaft can be mounted on the CNC milling machine, and the grooves can be milled according to the program. Each time a groove is formed, the shaft is rotated to move to the next position, and accurate angle setting is important at this time. Milling conditions can be adjusted to maintain a constant depth and width of each groove. After the groove machining is completed, the shaft surface can be polished to reduce roughness, and if necessary, heat treatment can be performed on the entire shaft to increase strength.

[0041]

[0042] In the post-processing step (S400), surface treatment and precision inspection can be performed on the material with the ball groove machined thereon. In the post-processing step (S400), surface treatment, precision inspection, and finishing treatment can be performed.

[0043] In the post-heat treatment step (S500), low-temperature heat treatment can be performed on the material after post-treatment. The post-heat treatment step (S500) is examined in more detail with reference to FIG. 3. Precision inspection is performed to precisely inspect the location, depth, width, etc. of the formed groove. This is carried out through measuring tools (e.g., micrometer, profile projector) and visual inspection.

[0044] Verify that all grooves meet specifications, and if defects are found, they can be reworked or corrected. For finishing, the necessary coating or surface treatment can be applied to the shaft, which is important for corrosion prevention and friction reduction.

[0045]

[0046] FIG. 3 is a flowchart illustrating a post-heat treatment step according to an embodiment of the present invention.

[0047] Referring to FIG. 3, a post-heat treatment step (S500) according to one embodiment of the present invention may include a heating step (S510), a quenching step (S520), and a tempering step (S530).

[0048] In the heating step (S510), the material that has undergone post-processing can be heated. In the heating step (S510), the shaft can be gradually heated to a set temperature. This step can be performed slowly to ensure uniform heating. Generally, the temperature used varies depending on the type of material and the desired mechanical properties, so the heating time may vary depending on the size and shape of the shaft.

[0049] In the quenching step (S520), the heated material can be quenched with a cooling medium. In the quenching step (S520), the shaft can be rapidly cooled after heating. Water, oil, polymer solution, etc., can be used as the cooling medium. Quenching can increase the hardness of the material and increase strength by changing its internal structure. In addition, care must be taken to ensure uniform cooling to minimize thermal stress that may occur due to rapid cooling.

[0050] In the tempering step (S530), the quenched material can be heated again to a preset temperature and slowly cooled. After quenching, the shaft can be heated again to a suitable temperature and slowly cooled. This step can increase the toughness of the material and relieve internal stress caused by quenching.

[0051] The tempering temperature is generally set between 150 and 700 degrees Celsius and may vary depending on the desired mechanical properties. The final mechanical properties of the shaft can be optimized by adjusting the tempering time.

[0052]

[0053] Referring again to FIG. 1, in the ultrasonic step (S600), ultrasonic vibration treatment can be applied to the material after post-heat treatment. The ultrasonic step (S600) will be examined in more detail with reference to FIG. 4.

[0054] FIG. 4 is a flowchart illustrating an ultrasonic step according to an embodiment of the present invention.

[0055] Referring to FIG. 4, the ultrasonic step (S600) may include a contact step (S610), a setting step (S620), a generation step (S630), and a cooling step (S640).

[0056] In the contact step (S610), the ultrasonic transducer can be brought into contact with the material.

[0057] In the setting step (S620), the amplitude and frequency of the ultrasonic vibration of the transducer can be set.

[0058] In the generation step (S630), ultrasonic waves can be generated using the transducer.

[0059] In the cooling step (S640), the heat generated during ultrasonic vibration can be cooled.

[0060] By providing the above ultrasonic step (S600), the breakage defect of the shaft can be prevented.

[0061] Referring again to FIG. 1, in the quality control step (S700), the surface roughness, hardness, residual stress, dimensional accuracy, and surface defects of the material after ultrasonic vibration treatment can be measured by a sensor unit to manage quality. In the quality control step (S700), precision, durability, and friction force can be evaluated. In addition, quality can be managed by storing all processing and inspection records.

[0062]

[0063] In addition, although not illustrated in the drawings, the method for forming a ball groove for a ball spline shaft according to one embodiment of the present invention may further include a fault diagnosis step (not illustrated).

[0064] In the fault diagnosis stage, the output data of the sensor unit is analyzed in real time, and if the instantaneous rate of change of the output data is greater than or equal to a preset value, it can be determined that a fault has occurred in the sensor unit.

[0065] To this end, in the first embodiment, the instantaneous rate of change (R) of the output data change Calculate ) and the above instantaneous rate of change (R change ) is a preset limit value (S err If it is greater than ), it can be determined that an error has occurred in the real-time output data of the sensor unit (e.g., due to a failure of the sensor itself).

[0066] Instantaneous rate of change (R) of sensor output datachange ) can be calculated through the derivative f'(x) of the function f(x) representing the characteristics of the sensor unit as shown in [Mathematical Formula 1] below.

[0067] [Mathematical Formula 1]

[0068]

[0069] Here, R change represents the instantaneous rate of change of the output data above, and △t represents the time change.

[0070]

[0071] In the second embodiment, the instantaneous rate of change of the sensor unit calculated in [Equation 1] above is a preset limit value (S err It can be determined that a failure has occurred in the sensor unit only when the number of times greater than ) is greater than a preset number of times during a preset period. In other words, since it is unreasonable to determine that a failure in the sensor unit has occurred even in cases where the instantaneous rate of change is high on a one-time basis, a standard can be set so that a failure in the sensor unit is determined only when the number of times greater than a preset number of times during a preset period is greater than ) in order to improve the accuracy of determining sensor failure.

[0072]

[0073] In the third embodiment, the instantaneous rate of change of the sensor unit calculated in [Equation 1] above is a preset limit value (S err It can be determined that a failure has occurred in the sensor unit only when the cumulative number of cases greater than ) is greater than or equal to a preset number. This is because, similar to the second embodiment, it is unreasonable to determine that a failure has occurred in the sensor unit even in cases where the instantaneous rate of change is high in a single instance, and rather than setting a preset period, the criterion is to determine that a failure has occurred in the sensor unit only when the cumulative number of cases from the operation of the sensor unit to the present time is greater than or equal to a preset number.

[0074]

[0075] In the fourth embodiment, if the change in the instantaneous rate of change of the sensor unit calculated in [Equation 1] above occurs rapidly, it can be determined that a failure has occurred in the sensor unit.

[0076] To do this, f''(x) calculated in [Equation 1] is differentiated again to calculate f''(x), and if the value is greater than or equal to a preset value, it can be determined that a fault has occurred in the sensor unit.

[0077]

[0078] Meanwhile, in the fifth embodiment, even if it is determined that a failure has occurred in the sensor unit through any one of the first to fourth embodiments, the sensor failure is not immediately confirmed, and the failure in the sensor unit may be confirmed when the 'sudden data occurrence condition' described below is simultaneously satisfied.

[0079]

[0080] Here, the condition for the occurrence of sudden data is to calculate the slopes of the upper line (810, 910) connecting the upper limit values ​​of the output data and the lower line (820, 920) connecting the lower limit values ​​of the output data, as illustrated in FIGS. 5 and 6, and if the difference in slopes calculated in [Equation 2] is greater than or equal to a preset value, it can be determined that sudden data has occurred.

[0081] Accordingly, at the same time as it is determined that a failure has occurred in the sensor part through any one of the first to fourth embodiments above, the slope difference (I) calculated in [Equation 2] diff It may also be set to confirm a failure of the sensor unit if the condition for sudden data generation is satisfied because ) is greater than or equal to a preset value.

[0082] [Mathematical Formula 2]

[0083]

[0084] Here, I maxis the slope of the upper limit line connecting the upper limit values ​​of the above output data, I min is the slope of the lower limit line connecting the lower limit values ​​of the above output data, I diff represents the slope difference (absolute value) respectively.

[0085] More specifically, as shown in FIGS. 5 and 6, sensor data is collected at regular intervals, and after calculating the slopes of the upper line (810) connecting the upper part of the collected data and the lower line (820) connecting the lower part, the difference in slopes (I) of the two lines diff If the difference is not significant (less than the preset value) when ) is calculated, it is determined that the sensor data is moving within the error range and that normal operation is being judged, and the difference in slope between the two lines (I diff If ) increases beyond a preset value, it can be determined that a malfunction has occurred in the sensor unit, as inaccurate values ​​are being output due to a malfunction in the sensor unit.

[0086] That is, in the case of FIG. 5, since the slope of the upper line (810) is 0.26 and the slope of the lower line (820) is 0.24, the difference in slopes (I) between the two lines diff ) is 0.02, and since this is smaller than the preset reference value of 0.12, it can be determined that the sensor is operating normally.

[0087] Meanwhile, in cases where the upper or lower line appears as a broken line, the slopes can be compared by dividing the area at each bend of the line or by calculating the average of the slopes within a certain period.

[0088] Referring to Fig. 6, we will first explain the case where the slope is compared by dividing the area at each bending section of the straight line. In FIG. 6, if the upper limit line (910) is composed of three lines, and the slope of the first line (911) is 0.26, the slope of the second line (912) is 0.45, the slope of the third line (913) is 0.38, and the slope of the lower limit line (920) is 0.24, then the difference in slope (0.26-0.24) between the first line (911) and the lower limit line (920) is 0.02, which is smaller than the preset reference value of 0.12, so it is judged to be operating normally; however, the difference in slope (0.45-0.24) between the second line (912) and the lower limit line (920) is 0.21, which is larger than the preset reference value of 0.12, so it is judged to be operating abnormally; and in the case of the third line (913), the slope between the lower limit line (920) and the Since the difference (0.38-0.24) is 0.14, which is greater than the preset threshold value of 0.12, it can be determined that the operation is abnormal. In this case, where the area is divided at each bend of the straight line to compare the slopes and determine whether a failure has occurred, the time at which the failure occurred can also be estimated, making it very useful when the time of failure needs to be identified.

[0089] Next, the slope can be compared by calculating the average slope within a certain period. In the entire section of FIG. 6, the average slope of the upper line (910) is {(0.24+0.45+0.38) / 3}=0.35, and since the difference from the average slope (0.24) of the lower line (920) is 0.11, it is smaller than the preset reference value of 0.12, so it can be determined that it is operating normally. In this way, determining whether there is a failure by calculating the average slope within a certain period does not determine it as a failure even if there are temporary slope fluctuations, as long as the average value does not exceed the reference value. This allows the sensitivity of failure determination to be lowered somewhat, thereby preventing unnecessary failure determinations.

[0090]

[0091] As seen above, according to one embodiment of the present invention, the number of ball grooves is increased to 12, and the effect of preventing breakage defects while simultaneously strengthening durability is achieved.

[0092]

[0093] As described above, although an embodiment of the present invention has been explained by limited embodiments and drawings, the embodiment of the present invention is not limited to the embodiments described above, and various modifications and variations are possible from this description by those skilled in the art to which the present invention pertains. Accordingly, an embodiment of the present invention should be understood only by the claims described below, and all equivalent or analogous variations thereof shall be considered to be within the scope of the inventive concept.

Claims

1. A preparation step (S100) for preparing a pipe-shaped material and aligning the center; A pre-heat treatment step (S200) of performing spheroidizing heat treatment on the above material with aligned centers; A groove forming step (S300) of forming 12 ball grooves in the above material after preheat treatment; A post-processing step (S400) for performing surface treatment and precision inspection on the above material with ball grooves processed; A post-heat treatment step (S500) of performing low-temperature heat treatment on the above material after post-treatment; An ultrasonic step (S600) of performing ultrasonic vibration treatment on the above material after post-heat treatment; and A quality control step (S700) for managing quality by measuring the surface roughness, hardness, residual stress, dimensional accuracy, and surface defects of the above material after ultrasonic vibration treatment using a sensor unit; A method for forming a ball groove for a ball spline shaft including 2. In Paragraph 1, After the above preheat treatment step (S200), An undercut step (S250) for forming an undercut on the above material after preheat treatment; A method for forming a ball groove for a ball spline shaft, further comprising 3. In Paragraph 2, The above post-heat treatment step (S500) is, A heating step (S510) for heating the above material after post-processing; A quenching step (S520) of quenching the heated material with a cooling medium; and A tempering step (S530) of reheating the quenched material to a preset temperature and slowly cooling it; A method for forming a ball groove for a ball spline shaft including 4. In Paragraph 3, The above ultrasonic step (S600) is, A contact step (S610) of contacting the ultrasonic transducer with the above material; A setting step (S620) for setting the ultrasonic vibration amplitude and frequency of the above transducer; A generation step (S630) of generating ultrasound with the above transducer; and A cooling step (S640) for cooling the heat generated during ultrasonic vibration; A method for forming a ball groove for a ball spline shaft including 5. In Paragraph 4, A fault diagnosis step for analyzing the output data of the sensor unit in real time and determining that a fault has occurred in the sensor unit if the instantaneous rate of change of the output data is greater than or equal to a preset value; Includes more, In the above fault diagnosis step, The instantaneous rate of change (R) of the above output data change Calculate ) and the above instantaneous rate of change (R change ) is a preset limit value (S err If it is greater than ), it is determined that an error has occurred in the sensor's real-time output data, and the instantaneous rate of change (R change A method for forming a ball groove for a ball spline shaft, characterized by calculating the derivative value f'(x) of the function f(x) representing the characteristics of the sensor part as shown in [Mathematical Formula 1] below. [Mathematical Formula 1] (Here, R change represents the instantaneous rate of change of the above output data, and △t represents the time change.

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