A machining method of a built-up inner spline shaft

Abstract

The application discloses a machining method of an assembled inner spline shaft and relates to the technical field of transmission shaft machining.The machining method comprises the following steps: firstly, processing an inner spline sleeve to a finished state to ensure that the outer circle of the inner spline sleeve is coaxial with the mounting shaft section thereon; performing semi-finishing machining on the outer circle of the spline shaft body and reserving a combined machining allowance; secondly, heating the spline shaft body to make the inner holes at both ends of the spline shaft body expand due to heat, hot-mounting the mounting shaft section into the inner holes at both ends of the spline shaft body, and reserving the spline shaft body after cooling; then, inserting a chuck tool into the spline inner holes at both ends of the inner spline shaft and fastening the chuck tool to obtain an assembled part; and finally, clamping the assembled part to a lathe, taking the outer circle of the inner spline sleeve as a reference to perform alignment, and performing finish machining on the outer circle of the spline shaft body after ensuring that the references at both ends coincide with each other.The application improves positioning accuracy by cooperation of the chuck tool and the inner spline sleeve, adopts a reference coincidence machining method, ensures coaxialities of the outer circles of the inner spline shaft with the large interference connection structure at both ends, and significantly improves overall machining accuracy.

Description

Technical Field

[0001] This invention relates to the field of transmission shaft machining technology, and in particular to a machining method for an assembled internal spline shaft. Background Technology

[0002] Splined shafts are a common type of transmission component in rolling mill equipment. In heavy machinery such as heavy plate rolling mills, the ends of splined shafts are typically designed with external splines to stably transmit torque during operation. Taking a 5600mm heavy plate rolling mill as an example, the stand rolls used there are one of the key components in the rolling process. During rolling, the front and rear work roller tables cooperate with the stand rolls to accurately feed the steel billet between the relatively rotating upper and lower work rolls for rolling, thus requiring high transmission smoothness.

[0003] Currently, traditional splined shafts are mostly integral structures. However, in large, heavy plate rolling mills, a new assembled internal splined structure has emerged to facilitate manufacturing, installation, and maintenance. This structure consists of a splined shaft body and an internal splined sleeve, with a large interference fit between them to achieve effective torque transmission. Due to the high requirements for transmission smoothness of the mill stand rolls, the outer circle of the splined shaft body and the inner hole of the internal splined sleeve must have a high degree of coaxiality to ensure the overall transmission accuracy and operational reliability after assembly. The traditional processing method for such parts is to process the splined shaft body and the internal splined sleeve separately into finished products and then assemble them together using a heat-fitting method. Due to the heat deformation that occurs during heat fitting, the coaxiality of the splined shaft body and the two internal splined sleeves is affected by thermal deformation after the splined shaft body and the internal splined sleeves at both ends are significantly reduced in accuracy. In addition, internal splined shafts are usually machined by gear shapers, but due to the large size of the assembled parts, it is impossible to perform a second gear shaper on a machine tool to improve accuracy.

[0004] Therefore, considering the structural characteristics and usage requirements of the aforementioned assembled internal spline shaft, there is an urgent need to propose a machining method that can ensure a high-precision coaxial fit between the spline shaft body and the internal spline sleeve. This application innovates a machining method for assembled internal spline shafts, effectively improving the machining accuracy of this type of frame roll with an assembled internal spline shaft structure, and meeting the high-performance requirements of heavy plate rolling mills for key transmission components. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a machining method for an assembled internal spline shaft, which can effectively ensure the high coaxiality between the outer circle of the spline shaft body and the inner hole of the internal spline sleeve, and improve the machining accuracy and transmission stability of this type of frame roller.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for machining an assembled internal spline shaft, the internal spline shaft comprising a spline shaft body and internal spline sleeves installed at both ends of the spline shaft body; one end of the internal spline sleeve has an installation shaft section that inserts into the inner holes at both ends of the spline shaft body, and the other end has a spline inner hole; the machining method includes the following steps: S1. Machining the inner spline sleeve to the finished state, ensuring that the coaxiality between the outer circle of the inner spline sleeve and the mounting shaft section is 0.02mm; the outer circle of the spline shaft body is semi-finished, leaving a machining allowance for assembly; S2. Heat the spline shaft body in a heating furnace to make the inner holes at both ends of the spline shaft body expand due to heat. Then heat-install the mounting shaft section of the inner spline sleeve into the inner holes at both ends of the spline shaft body and cool it to room temperature to obtain the assembled inner spline shaft. S3. Insert the chuck fixture into the spline inner holes at both ends of the internal spline shaft and connect and fix it with fasteners to obtain the internal spline shaft to be precision machined. S4. Mount the internal spline shaft to be precision machined onto the lathe. Using the outer circle of the internal spline sleeve as a reference, align the two finished inner spline sleeve outer circles with an alignment accuracy of 0.05mm. After ensuring that the two references coincide, precision machine the outer circle of the spline shaft body to ensure the overall machining accuracy of the internal spline shaft.

[0007] Further, in step S3, the chuck fixture includes a clamping sleeve and a splined shaft head. The clamping sleeve has an inner hole that precisely matches the outer circle of the inner spline sleeve, and the inside of the clamping sleeve is provided with an inner square groove. The splined shaft head is provided with an outer square protrusion that matches the inner square groove, and the splined shaft head is also provided with an outer spline that matches the inner spline of the inner spline sleeve. The clamping sleeve and the splined shaft head are connected and fixed by fasteners; the fasteners are bolts.

[0008] Furthermore, the inner hole of the clamping sleeve and the outer circle of the inner spline sleeve are precisely fitted for clamping and positioning; the fit between the outer square protrusion and the inner square groove, as well as the fit between the outer spline and the inner spline, together constitute the torque transmission path.

[0009] Furthermore, in step S1, the coaxiality between the inner hole of the spline and the outer circle of the inner spline sleeve is 0.04 mm.

[0010] Furthermore, in step S1, the finished precision of the inner spline sleeve is grade 6.

[0011] Furthermore, in step S2, the heating furnace is heated to 250℃-260℃ for 2 hours; the inner holes at both ends of the spline shaft body expand by 0.4mm after being heated.

[0012] Furthermore, in step S4, the alignment refers to using a dial indicator to check the outer diameter of the inner spline sleeve at both ends, and adjusting it so that the runout at both ends does not exceed 0.05mm.

[0013] According to the above technical solution, the beneficial effects of the present invention are: This invention improves the positioning accuracy of the chuck by precisely fitting the inner hole of the clamping sleeve with the outer circle of the inner spline sleeve. Inside the chuck, a four-way fit structure is used between the clamping sleeve and the spline shaft head. Torque is transmitted through this four-way fit and the inner and outer splines, replacing the conventional method of torque transmission via bolts in the chuck. This effectively avoids the risk of bolt shearing and improves the reliability of torque transmission during turning. Simultaneously, a datum coincidence machining method is employed, ensuring both the coaxiality of the outer circles of the inner spline shaft in this type of large interference fit connection structure and the coaxiality of the inner holes of the splines at both ends. Through the effective synergy of the chuck and the datum coincidence machining process, the overall machining accuracy of the inner spline shaft in the large interference fit connection structure is significantly improved. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the inner spline sleeve structure of the present invention; Figure 3 This is a schematic diagram of the clamping outer sleeve structure of the present invention; Figure 4 for Figure 3 The right view; Figure 5 This is a schematic diagram of the splined shaft head structure of the present invention; Figure 6 This is a cross-sectional view (AA) of the spline shaft head of the present invention; Figure 7 This is a schematic diagram of the clamping fixture installation according to the present invention.

[0015] The markings in the diagram are: 1. Lathe chuck, 2. Lathe center, 3. Splined shaft body, 4. Clamping sleeve, 5. Inner spline sleeve, 51. Mounting shaft section, 52. Splined inner hole, 6. Splined shaft head. Detailed Implementation

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

[0017] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0018] like Figure 1-7As shown, a method for machining an assembled internal spline shaft is described. The internal spline shaft includes a spline shaft body 3 and internal spline sleeves 5 installed at both ends of the spline shaft body 3. One end of the internal spline sleeve 5 has a mounting shaft section 51 that inserts into the inner holes at both ends of the spline shaft body 3, and the other end has a spline inner hole 52. This invention involves multi-part assembly and requires high precision.

[0019] The processing method of the present invention includes the following steps: S1. The inner spline sleeve 5 is machined to a finished product with a precision grade of 6. The coaxiality between the outer circle of the inner spline sleeve 5 and the mounting shaft section 51 is 0.02mm, and the coaxiality between the spline inner hole 52 and the outer circle of the inner spline sleeve 5 is 0.04mm. The outer circle of the spline shaft body 3 is semi-finished, with a machining allowance reserved for assembly.

[0020] S2. The spline shaft body 3 is placed in a heating furnace and heated at a temperature of 250℃-260℃ for 2 hours, so that the inner holes at both ends of the spline shaft body 3 expand due to heat. The expansion amount of the inner holes at both ends of the inner spline shaft body 3 after heating is 0.4mm. Then, the mounting shaft section 51 of the inner spline sleeve 5 is heat-installed into the inner holes at both ends of the spline shaft body 3 and cooled to room temperature to obtain the assembled inner spline shaft.

[0021] S3. Insert the chuck fixture into the spline inner holes 52 at both ends of the internal spline shaft and connect and fix it with fasteners to obtain the internal spline shaft to be precision machined. Preferably, the fasteners are bolts.

[0022] It should be noted that the chuck fixture includes a clamping sleeve 4 and a splined shaft head 6. The clamping sleeve 4 has an inner hole that precisely fits the outer circle of the inner splined sleeve 5, and the inside of the clamping sleeve 4 is provided with an inner square groove. The splined shaft head 6 is provided with an outer square protrusion that fits with the inner square groove, and the splined shaft head 6 is also provided with an outer spline that fits with the inner spline of the inner splined sleeve 5. The clamping sleeve 4 and the splined shaft head 6 are fixed together by bolts. The fit between the outer square protrusion and the inner square groove, as well as the fit between the outer spline and the inner spline, together constitute the torque transmission path.

[0023] This invention improves the positioning accuracy of the chuck by precisely fitting the inner hole of the clamping sleeve 4 with the outer circle of the inner spline sleeve 5. Inside the chuck, the clamping sleeve 4 and the spline shaft head 6 are connected by a four-way mating structure. Torque is transmitted through the four-way mating and the inner and outer splines, replacing the conventional method of transmitting torque with bolts in the chuck. This effectively avoids the risk of bolt shearing and improves the reliability of torque transmission during the turning process.

[0024] S4. Mount the internal spline shaft to be precision machined onto the lathe. During mounting, the lathe chuck 1 grips the outer diameter of the clamping sleeve 4, and the lathe center 2 presses against the inner hole of the clamping sleeve 4. Using the outer diameter of the internal spline sleeve 5 as a reference, align the finished inner spline sleeve 5 outer diameters at both ends. Specifically, alignment means using a dial indicator to check the outer diameters of the inner spline sleeve 5 at both ends and adjusting them until the runout at both ends does not exceed 0.05mm, i.e., the alignment accuracy is 0.05mm. After ensuring that the references at both ends coincide, precision machine the outer diameter of the spline shaft body 3 to ensure the overall machining accuracy of the internal spline shaft.

[0025] This invention ensures the coaxiality of the outer circles of the internal spline shaft in this type of large interference fit connection structure at both ends, and also ensures the coaxiality of the inner holes 52 of the splines at both ends. Addressing the practical problem that internal spline shafts are typically machined by gear shapers, but cannot be re-machined on a machine tool to improve accuracy after assembly due to the large size of the parts, this invention effectively improves the machining accuracy of the internal spline shaft in high-precision combined ultra-long interference fit connection structures. Through the effective synergy of the chuck tooling and the datum coincidence machining process, the overall machining accuracy of the internal spline shaft in the large interference fit connection structure at both ends is significantly improved.

[0026] It should be noted that the above embodiments are only used to illustrate the present invention, but the present invention is not limited to the above embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for machining an assembled internal spline shaft, the internal spline shaft comprising a spline shaft body (3) and internal spline sleeves (5) installed at both ends of the spline shaft body (3), one end of the internal spline sleeve (5) having an installation shaft section (51) that inserts into the inner holes at both ends of the spline shaft body (3), and the other end having a spline inner hole (52), characterized in that, The processing method includes the following steps: S1. Machining the inner spline sleeve (5) to the finished product state, ensuring that the coaxiality between the outer circle of the inner spline sleeve (5) and the mounting shaft section (51) is 0.02mm; semi-finishing the outer circle of the spline shaft body (3) and reserving the assembly machining allowance; S2. Heat the spline shaft body (3) in a heating furnace to make the inner holes at both ends of the spline shaft body (3) expand due to heat. Then heat the mounting shaft section (51) of the inner spline sleeve (5) into the inner holes at both ends of the spline shaft body (3) until it cools down to room temperature to obtain the assembled inner spline shaft. S3. Insert the chuck fixture into the spline inner holes (52) at both ends of the inner spline shaft and fix it with fasteners to obtain the inner spline shaft to be precision machined; the chuck fixture includes a clamping sleeve (4) and a spline shaft head (6). The clamping sleeve (4) has an inner hole that precisely matches the outer circle of the inner spline sleeve (5), and the clamping sleeve (4) has an inner square groove inside; the spline shaft head (6) has an outer square protrusion that matches the inner square groove, and the spline shaft head (6) also has an outer spline that matches the inner spline of the inner spline sleeve (5); the clamping sleeve (4) and the spline shaft head (6) are fixed together by fasteners; S4. Mount the inner spline shaft to be precision machined onto the lathe. Using the outer circle of the inner spline sleeve (5) as a reference, align the inner spline sleeve (5) at both ends in its finished state. The alignment accuracy is 0.05mm. After ensuring that the references at both ends coincide, precision machine the outer circle of the spline shaft body (3) to ensure the overall machining accuracy of the inner spline shaft.

2. The machining method for the assembled internal spline shaft according to claim 1, characterized in that: In step S3, the fastener is a bolt.

3. The machining method for the assembled internal spline shaft according to claim 2, characterized in that: The inner hole of the clamping sleeve (4) and the outer circle of the inner spline sleeve (5) are precisely fitted for clamping and positioning; the fit between the outer square and the inner square, as well as the fit between the outer spline and the inner spline, together constitute the torque transmission path.

4. The machining method for the assembled internal spline shaft according to claim 1, characterized in that: In step S1, the coaxiality between the inner hole (52) of the spline and the outer circle of the inner spline sleeve (5) is 0.04 mm.

5. The machining method for the assembled internal spline shaft according to claim 1, characterized in that: In step S1, the finished precision of the inner spline sleeve (5) is grade 6.

6. The machining method for the assembled internal spline shaft according to claim 1, characterized in that: In step S2, the heating temperature of the heating furnace is 250℃-260℃ and the heating time is 2 hours; the expansion of the inner holes at both ends of the spline shaft body (3) after heating is 0.4mm.

7. The machining method for the assembled internal spline shaft according to claim 1, characterized in that: In step S4, the alignment refers to using a dial indicator to check the outer diameter of the inner spline sleeve at both ends, and adjusting it so that the runout at both ends does not exceed 0.05mm.

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